Forgiveness takes a lot of faith, and that faith comes more easily if we are not fully buying into the system of separation. But it also has to do with the heart.
Often it is an intuitive flash that tells us that not forgiving, but holding vengeful, hateful thoughts, is actually more damaging to our own system. This poison of hate and resentment will also affect the person we are projecting those thoughts onto, but in the end it is going to hurt us more.
So forgiveness is the willingness to let go--of our self-importance, our pride, our hurt, our resentment, and the feeling that we have to get our pound of flesh.
Deep inside us we do know the truth, that we are not separate and that we are love. When we awaken to the truth, about our real self and thus to love, we do not proudly and self-importantly pamper and cherish ourselves. We love ourselves in a much more respectful way, all the while knowing that our and others' baggage does not matter. It does not have to be important. That is true nobility of soul.
As Alexander Pope said, "To err is human, to forgive divine." Learning to forgive is the very real awakening of our divine nature.
Source: Returning to Oneness, by Leslie Temple-Thurston with Brad Laughlin (CoreLight Publishing, 2002)