Somehow, we have the impression that we can forget the past, especially our painful past. We misinterpret Philippians 3:13 where Paul says "Forgetting what lies behind me and striving forward to what lies ahead, I press on toward the goal for the prize of the upward call of God in Christ Jesus" and think this means we just need to forget the past and become some super-Christian who is only concerned with what lies ahead. First of all, that's not a proper understanding of the verse. Paul has just listed all of the reasons he could be confident in the flesh, but is pointing out that this doesn't mean anything in comparison to what God has for us in Christ Jesus.
Honestly, we will never be able to forget the past, but thanks to God we can get past the past. Those vivid mental snapshots from long ago may never be erased from your memory bank, but they don't have to label you.