Memories are just moments pieced together. A moment in time can be forever embedded in your mind, so keep the good memories alive and forget about all those bad moments. You control your thoughts, don't let them control you.
Usually, it seems to take huge doses of forgiveness for me to move past the bad moments. I don't want to live there, in a prison of disappointment, fear, shame, unforgiveness when the opposite is available to me. I want to choose life.
Keep the BEST memories alive. What moments are you building your future on and where are you currently living?
Philippians 4:8, "...whatever things are true, whatever things are noble, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report, if there is any virtue and if there is anything praiseworthy—meditate on these things."