Holding on.

I've suffered with depression for a super long time. I'm tired, annoyed, angry. I just want to be happy! Some people say hapiness is a choice. For a depressed person, well atleast for me it's not. I try so hard(maybe not hard enough) to be happy, but I can't. I just can't. It feels like my brain won't let me. The moment I feel sort of happy I feel like there's something wrong. Something missing. I was thinking, maybe what's stopping me from being happy is all the anger I have. All the anger I feel towards my dad, my mom, life, the people that bullied me, and myself. But how do I let go? I try and try and try and try to let go and not be angry, but it's hard. How can I not feel anger towards the people that ruined my life. How can i not be mad at all the shit my dad has said to me and done. How can i not be mad at my mom for never standing up for herself and me. Why do I keep believing in all the things people say about me and not believe what I know about myself? Why can't I let go of all the anger I have!? Why is it easier holding on to all this anger that keeps building up than letting go?