Wow that is an incredibly difficult yet profound question. So far life has taught me that everything is fluid and constantly changing even in the most minute ways, sometimes in huge ways, I've learnt that the people I looked to as a child and thought knew everything make mistakes too. I've learnt to embrace and be grateful for all the things and people I have in my life as you never know if they will be around tomorrow. I am trying to wear my heart on my sleeve and show and tell people how appreciative I am that they are in my life. But life has a way off pulling you away from the important things and into the mundane.
My friend gave me this many years ago and it still holds relevance, even more so as I get older.