There is no solution to discipline other than discipline.
You must set a clear goal and then work towards it every day, building momentum over time. For this, vision is very important.
But in the end, you must....
JUST DO IT!
Start small and ramp your way up over the weeks, months, and years. If it was easy, everyone would be mega-successful. No one else can do it for you and there are no shortcuts or magic pills. You gotta have the courage to bite the bullet and endure some emotional labor and discomfort.
The key is consistency. You must chip away at it every day and not bite off more than you can chew.

NoFap + meditation and studying why women will never make you happy in the long run.
Unless you find a girl you REALLY like, you won't chase anything anymore.

One of Leo's most popular videos is the one titled -How to stop caring what others think of you?- in fact that is the video that introduced me to his content. When I first watched that video one and a half years ago it re-energized me and I was ready to use this knowledge to better my life, but I was not expecting immediate results. I became icy and I really did not care about making friends with everybody. What I noticed was that most the girls paid more attention to me and more guys took me seriously, I kept that attitude going for a couple of weeks, but much later I fell back into being needy again. (It was miserable)
Again another school year begins this time I decide to be extra nice (extroverted), care for everyone. This guise of mine didn't last very long because no one was paying attention to me. But one day I arrived extra icy, caring very little about what people thought of me. Again I got more attention and respect. This lasted for a couple more weeks and then I went back to my usual self.
I know Leo emphasized on affirmations and how they help change the way you think, do they really work?
Is there another possible technique I could apply? And whenever you guys are needy, how do you get back on track?
PS -While typing this I noticed that my although my intention should be to stop caring of what others think of me, I am still using the technique to get attention from others. This is kind of contradictory to the purpose of this excercise, is this "need" deeply lodged into me psychologically changable?

I think you're addicted to activities that give you pleasure. As you said earlier, Youtube videos is exciting and enjoyable for you, so you prefer to do that than studying. This could mean that you're addicted to pleasure and want immediate gratification, and so studying is not a pleasurable activity for you
So I say find something in studying that is enjoyable, the same enjoyment you do with Youtube videos or any other activity you enjoy. I think you see studying as more of a chore, and you probably realise that this view causes tension.
The fact that it's a chore and something you hate is something based on your view of studying. If you see studying as something you don't like and hate, of course you will resist. Self-actualization can be seen as a study, so why do you not hate studying this?
Try and do some self-inquire on why you're not enjoying it. So like... Is it too easy? Too hard? Won't ever need this in my career? This is all bullshit? Try and ask yourself these questions. Rather than inquiring resistance, inquire about why you're not finding this enjoyable like watching movies?
To really create habits, I think you just have to clear your mind and stop thinking about "what to do" and just do it. Be a robot

Lol, this isn't exactly a big secret. Basically all guys suck at talking with women unless they trained that skill.
You should approach even if you are not relaxed or "in state". Sure, you will blow up sets, but it doesn't matter because blowing up sets is what gets you to relax.
Never expect your first approach of the day to go smooth. The first few approaches are just warm ups. They almost always blow up. If you're approaching, you should be doing at least 10-20 approaches within a few hours. Once you blow the first 10, then you'll hit state and you will start acing the rest.
The key to learning game is to find a location where you can do 10-20 approaches within a few hours. Find an area with tons of girls so that you aren't worried about blowing sets up. Become an approach machine for a while and your skills will skyrocket.
I remember when I approached 750 girls in one month. That was a productive month! You'll be amazed at what opportunities materialize from 750 approaches. The most unlikeliest of things pan out with those numbers. If you approach 750 girls, one of them will just want to suck your dick for no reason at all, LOL. Most guys don't meet that many girls in their entire lifetime. You can do it in one month.

I got a lot of addictions smoking tabbaco, drinking soda, and I would say internet but, I seen a recent topic on that. One problem with internet is i don't exercise i spend time on internet. tabbaco and nicotine is the hardest cause I always want it.

In my situation is my own race where I'm picking up the bad vibe between us. One of Leo's video's i found helpful.  "How to stop caring what people think of me". He basically said 1 in a 100 people will just hate you for no apparent reason. 
It's just ridiculous how some people are.
 

This is the starting point for a lot of personal development work: how do I make change?
If we could make all the change that we wanted to, personal development would be unnecessary.
My advice is to single out the change you want to make very clearly.  Set it as a project.  Take baby steps to execute it.  Break the project down into steps or stages if possible.  You also want to know why you're doing what you want to do and what kind of long-term effect it will have.   Then you need a way to hold yourself accountable to chipping way at it.  For example, make a daily checklist that you print out every day that has the work to be done that day which you cross off when completed.  And then also you might want to experiment with doing some reprogramming of your Ego-Mind with positive affirmations to get your Ego-Mind bought-in to what you want to do.  That's important.  If your Ego-Mind is against what you want to do, that's like swimming against a current.  And when you start taking action, you'll build up a little momentum which is important too.  Oftentimes once you get started on a project, the hardest part of the project will be done -- because getting started is the hardest part because the Ego-Mind is not convinced that what you're doing is a good thing: that fear kicks in and blocks you.  Oftentimes you hear the cliche, "getting started is the hardest part of a project".  That's true!  So, get started, break your project down, take baby steps, and build that momentum slowly.

Thanks for explaining your point of view. You are right, and adding an important aspect. 
I do agree, and if I encounter a girl who is clear about that, and just want to have sex for entertainement, not necessarily in name of "true love", well I won't hesitate a second... If she is clear about it.
It's just that the girls I encounter don't think like that, they are also looking for "the one". I see that there are a lot of lies involved in the realtionships today. Few peoples are being 100% honest ; they lie to the other one and to themselves. 
If I try to seduce a girl just for fun, if it's a superficial kind of girl, I have to lie to her and to myself. I just want to be honest and truth, I don't want to tell her stuff I don't really think. I don't want to lie to anybody. I do have desires, but if I need to lie in order to fulfill them, that's ridiculous for me. I'm sure life is going to giving me the posibility to live sex while being truth with her and myself. It can be in name of true love, or in name of simple entertainement, but truthfully.
 
 

Well, MonikaBcn... The truth for me is that I don't really know what to think about sex, and I don't really want to think about it.
What I meant is that I don't feel that I need sex, so I won't go outside and seduce a girl just in order to have sex. For exemple, last november, I went to Balaguer's Fiesta mayor (Lleida, ES), and I spend the night with a couple of attractive girls; the girls in spain are much more open than french girls, and they seemed much easier to seduce... But they were all too superficial... I had a lot of fun, because I don't have fears anymore (thanks to the beautiful teachings of "simple-pick-up" and "simple sexy stupid")... But I didn't felt il love... at all... Well, it's kind of frustrating, because I'm 19, and all the girls I meet when I go out seems so blind to me... I know this is just judgements my ego is making... But I'm just not falling in love with girls who seems so blind to my ego.
One of my friends told me that when he had sex with someone he didn't really love, just in order to fulfill the need, he felt very bad abou it... that it didn't fulfilled him at all, and he feld disgusted about himself afterward, because it wans't truth for him. This discussion I had wit him impacted me. That's what i meant by "I would feel like a lier".
For now, I didn't felt in love for now, and I never had any opportunity to have sex (I mean, with someone I love)... And I totally accept it, I feel very good about it, and appart from the desire I have wen looking at a sexy girl, I don't feel any need. If one day I fall in love, I wont reject it, I will allow myself to fully live this experience. But if I don't, well, I will fully accept it as well, because I feel that's not a need for me. Just accepting whatever life give me, and follow the flow.
The discovering of truth ann enlightenment is the most important for me... It sex is on this path, I will accept it, great, if not, i will accept the absence of sex, great as well. 
 

The more you try to resist the emotion the stronger it gets and the more it will drive you insane. 
Identify the emotion. What is it? Jealous? Anger? Fear of loneliness? Fear of not finding a partner? Once you do, sit with it an open yourself up to the emotion. Feel it with every inch of your body as it flows through like an invisible snake. Do this until you become comfortable with the emotion. 
Once your body has had time to process it and identified it as not harmful but in a sense beautiful, it will naturally subside. 
If you resist it, it will torment you forever. 

I have the same problem. I also slack off with the habits I try to install. Especially meditation. 
Realize that persistance is KEY. If you fall off track, accept that. No one is perfect. But keep going because some people get discouraged when they fail. Somrtimes you need 100 tries to do somethimg succesfully. The 99 steps prior are just steppingstones leading to the 1 success that is the reward for your desire to keep fucking going. 

@Ryan_047 Leo has a video called "how to stop backsliding" which I assume is about this. Also the book Mastery by George Leonard talks about this topic of how to not backslide, falling off track briefly. The path of Mastery would help a lot too I feel. Also I would recommend motivating yourself with a vision that you can create for yourself. Leo has a good video called "true vision" and another called a "a vision for the self actualized life." Also motivational videos. I fall off on installing habits all the time haha. It's hard and can take time.  And also love and accept yourself. I sometimes have trouble with this too. We aren't perfect. Muster up the strength you need and go do it! Also getting energy would help. A life purpose would give you lots of energy so that would be a good place to start. And a gym routine and healthy diet would give you more energy.

I have a hard time in continuing my habits that I install for myself.I can't meditate for more than 3 months or do anything  consistently...
I have depression,and that is stopping me from doing a lot of things...I have no motivation and I don't feel any connection to anyone..I just don't really care about anything.Doing a good thing for you requires at least a little bit of motivation,therefore,I find it really hard to continue a habit on a daily basis.Also,please don't ask me about my depression here in this topic,because I know what I need to do in order to cure it and what caused it.I haven't wrote this having this purpose in mind...
As I was saying,I meditated for 3 months using just my will,so to speak...But then I fell of track and since then I'm spinning in a circle...Start a habit,fall of track..start a habit,fall of track..and so on.If I continue this way,I will never break out of depression...So,how can I force myself not to fall of track??Is there a technique other than forcing myself through will?