I have a confession to make. I'm a Master Composter, and....
My compost pile is an iceberg.
Yes, i know the heap is supposed to be hot, but mine is cold. Really cold. Frozen solid. I managed to scrape 2 inches off the top before i hit the frost line.
The trauma or suffering of our past can be just such frozen compost. If the old stuff from the past is still bothering you, begin with forgiveness. Forgiveness of yourself first of all. You might spend a day, a week, or a year forgiving yourself.
Later, you can practice forgiving the other person. (This does not mean that you condone the action.)
Without a foundation of forgiveness, our spiritual practice just spins its wheels.
Breathe in your suffering--that cold, dark, hard place--and breath out light and warmth to yourself. Fill yourself with light. Fill yourself with warmth and caring.
Light and warmth will thaw out that old compost pile.