In order to stop living in the past I believe you need to grieve it. The good, the bad, all of it. Grieve it, feel it (with a good therapist or support group etc) accept whatever part was yours, or not yours (I DONT MEAN ABUSE) forgive. I dont mean forgive horrible things so that person feels better I mean forgive the stuff thats blocking your path because forgiveness is for the forgiver imo. This process can be fast, slow, linger, languish... but one day you will wake up and the first thought of your day wont be about something horrible you think you did or are or were.