I have depression, anxiety, ADHD, and BPD. Most of my depressive episodes and negative thoughts circle around all the horrible things I've done. I've been a terrible, clingy, manipulative, jealous friend to a lot of people resulting in the loss of all but a few of my friendships, I've said horrible things to my family in fits of anger, I've taken things from my friends when I'm feeling spiteful and angry, I've sent mean text messages, and I can't live with myself when I get into a thought spiral of how horrible a person I am. 

I know I'm awful and probably don't deserve a good life, but I also know the only way to start trying to be a little happier is to let go of the past and forgive myself. My internal pain and self hatred causes a lot of these external mean things that I do and I want to let go of that but I don't know how. I know in my heart that I am kind and caring and empathetic a lot of the time, and a lot of people would describe me that way, but when my mental illness takes over, it turns me into a person I don't want to be, and I'm left feeling guilty for the rest of my life. I feel like a 500 pound weight is crushing me. What do I do?