"To err is human; to forgive, divine." ~ Alexander Pope
I've been reading that forgiveness is an instinct. A gift from evolution. Our ancestors would have had to develop the instinct to forgive so that they would survive in situations where cooperation was necessary for that survival. This makes sense in cases where people need each other. But the instinct to forgive in any situation would not be beneficial for survival. Thus the other instinct evolution has blessed us with - the instinct for revenge. Revenge would have been necessary to deter repeated violence against an individual or group.
|This is the pretty version...*|
Forgiveness is what Christ talked about throughout his ministry when he told us to love our enemies and forgive repeatedly those who wrong us. Forgiveness is the example he gave when, on the cross, beaten beyond recognition, suffering unimaginable pain, he forgave the ones who had put him there. And forgiveness is what Christ made possible when he died on that cross, taking the penalty for our sins, so we might have reconciliation with God.
Real forgiveness means we forgive when our instincts tell us to seek revenge. Real forgiveness is divine. And we are capable of it only because we are made in the image of God.
"Even if they sin against you seven times in a day, and seven times come back to you saying 'I repent,' you must forgive them." ~ Luke 17:4
"When they came to the place called the Skull, they crucified him there, along with the criminals—one on his right, the other on his left. Jesus said, 'Father, forgive them, for they do not know what they are doing.'" ~ Luke 23:33-35
*The beating Jesus got before he even got to the cross would have left the skin over his whole body ragged. He would not have looked this good. For a more accurate portrayal - one that I couldn't bring myself to even post because it's so graphic - look up photos from the movie The Passion.