Now I know why I was so angry!?

I meet up with my ex. We are now "friends", he has moved on , which as a friend I would have advised him against but hey. We went out a week ago and he made me angry. Not the first time but this time was different I just wanted the feelings of anger to stop. I just wanted to stop letting him control my emotions. I also read an article about divorce and that helped me as well. I was  hiding behind my anger to make him the bad guy, when in reality he isn't. He tried his best and he is trying his best to be the best dad. I want to control him  and because he is so pliable, think that he would go for it. Because he is so passive/aggressive I just think every suggestion I make he should take, but I cant control anyone and come to think of it I don't want to. We both tried our best and sometimes things don't work out, and I was angry at him because he was so slow to action but thats probably because he is scared and there is nothing wrong with being scared. I think he needs to work on his relationship with his daughter seeing her more and being more relaxed with her but its not my business. He will have to work on his relationship with her by himself and  I will be there for her if she needs me. I have to stop thinking I can change people and why would I want to. I'm too busy trying to fix/help myself. I give myself permission to not try to change anyone and to curb my anger.