Most of what we worry about is either in the past or the future - rarely in the NOW.

Living in the present moment is the key to forgiveness.

No past event can hurt you now - unless you let it; because all it is now is a thought.

"Where did we get the idea that if we don't forgive people, they suffer?"
Andrew Matthews

"There is only one perpetrator of evil on the planet: human unconsciousness. That realisation is true forgiveness. With forgiveness, your victim identity disolves, and your true power emerges - the power of presence. Instead of blaming darkness, you bring in the light"
Eckhart Tolle

The quickest route to inner peace is to stop thinking

If you cannot forgive totally in one go, try forgiving in stages; allow 10% forgiveness each day until you can build up to 100%. (From "The Power of Letting Go" by Patricia Carrington)

There are many Books to try including:

"Stop Thinking & Start Living" by Richard Carlson

“The Power of Letting Go"
by Patricia Carrington

"The Power Of Now"
by Eckhart Tolle