Sometimes you just have to make peace with whatever has happened in the past inorder to keep your present and future from becoming a constant battle. Leave the past in the past, those who dwell in the past don't last, they fade very fast. Let go of the things that drain the joy of today and steal the blessings of tomorrow. If you don't heal from the Hurts and wounds of the past, you are going to bleed on those who didn't cut you.
The past you didn't make peace with will keep showing up in the present. So accept whatever has happened, learn from it, and get on with your life.
The past is gone, Don't live in regrets, pick up the pieces you can get, and build again, this time stronger, better and wiser. What can't be changed should be endured, in your endurance, you find strength to do greater things. Make peace with your past, make the most of your present, and you will create a greater future. What's done is done, one of life's greatest lessons is to move on.