I am often intrigued by how saved I am yet battle with some old memories; it would appear that salvation - though it forgives the past, doesn't remove the memories of the past. Our past haunts us like they were never forgiven. The fight of faith (1 Timothy 6:12) is the fight that keeps training the mind to accept the past but deny its "driving" importance today. I can't keep beating myself over the head for the failures i had in my past; if I did I would never enjoy the very present opportunites for joy that are right before me. I understand that the devil does just that; he presents us with the opportunity to relive a forgiven past. We must refuse that invitation.
I read about a bunch of guys waiting for the Holy Spirit to come upon them in the early days of the church. Well, once the Holy Spirit came, He resided upon each and everyone of them (120 in number) as tongues of fire on their heads. I thought it was remarkable that the power was in their heads/minds moreso than anywhere else. In a rather simplistic way of looking at this bible text (Acts 2), I concluded that the power we receive from God is primarily worked out in our minds after which it plays out in our lives.
Well, I pray for you that God gives you that mental fortitude by the Holy Spirit to reject the invitation of the devil to relive a past that has been forgiven; you don't have to forget it for it to loose it's power over your life. In actual fact, remembering it but minimising it is what drains the power of that undesired memory.
Check out Acts 2 when you get a moment!