Forgiveness does not change the past, but it does enlarge the future.
When you hold resentment toward another, you are bound to that person or condition by an emotional link that is stronger than steel. Forgiveness is the only way to dissolve that link and get free.
The remarkable thing is that we really love our neighbour as ourselves: we do unto others as we do unto ourselves. We hate others when we hate ourselves. We are tolerant toward others when we tolerate ourselves. We forgive others when we forgive ourselves. We are prone to sacrifice others when we are ready to sacrifice ourselves.