The only tie you still have to a negative person or event in your past is your memory of it. The fact that you keep looking back and dwelling on this is what may be harming you emotionally, but you have control over that. By thinking a lot about that difficult time, you keep reliving it, and that is not necessary. You may not be able to forget what happened, but you can certainly forgive yourself and anyone else who may have had a role. You will always have the memory, but you don't have to keep the bad feelings associated with it if you can reframe it as a life lesson.