Never compare oneself or ones life to anyone else. Everyone is totally unique. Keep off Facebook...I hate it.
I've had bad periods in my life, truly. Nowadays I'm happy if I get sleep, it's wonderful. Every day I wake up I feel thankful that my body is well, that my organs and systems work, that I am not housebound or disabled or in hospital, that I have a home, food to eat. I take absolutely nothing for granted. To have your physical health is to have riches. Mental health takes some work for many of us.
It is going to sound trite but I take pleasure in sunshine, watching trees and flowers unfold, seeing a new puppy, a new baby, having a joke with someone in a shop, art, amazing books, music, good films, nature in general, walking through a park, hearing children playing and laughing...
In short, looking outwards to how much in the world is wonderful, clever and beautiful...and not inside to my despair, problems and worry, and to know that the vileness and awful, terrible things in the world are outweighed by the good.
It doesn't make it right, it doesn't take away your experiences but it helps to look at life from a different angle and perspective...and take yourself out of it all, be an observer.
I observe and appreciate and enjoy others happiness...I observe life, I appreciate what I do have and forgive myself for not having what I would have liked to have had. I accept I'm flawed but still enjoy the everyday small things. Now content, but it took a long time to get here. I hope you do OP.