Ego responses are about the pain we experience when we perceive a situation that somehow triggers the inferiority and superiority of ego. Each one of these perceived slights adds to and builds up the pool of karma surrounding our soul or that relationship.
When you forgive you release the ego emotions affiliated to that event, you release yourself from having to relive and resolve the issue on the karmic level. Basically, forgiveness creates a collapse of time that means that future events do not have to occur in order to redress the imbalance.
With every step you take along the path to forgiveness, you release more and more of your ego until your soul finally has control of what is happening in your world.