I deleted my FB account. Got sucked back into it. Then deleted it again.
You will be amazed how many times a day you go on FB without thinking. When I just deleted my account I found my self going to the FB page many times a day on auto-pilot and get the screen my account had been deleted, lol.
I agree there is a lot of negativity on FB. But even when I read something positive or somewhat neutral information, it's still an external source of information that I can do without.
It's a lot of external impulses that consequently will steer your mind in a certain direction, now you have to think about that information, process it, and those thought patterns lead to other spin-off thought patterns. All triggered by an external source that you got exposed to but didn't really volunteer for.
When I am not on FB I think my mind is more at peace, focused, and there is more room for thoughts and ideas that come up internally, that are my own.