"What gives so much force to the impulse of anger in such cases is the overwhelming sense that the offender does not deserve forgiveness. That is, the grievance is so deep and so justifiable that not only does self-righteousness strengthen our indignation but so does a legitimate sense of moral outrage. It's the deep sense of legitimancy that gives our bitterness its unbending compulsion. We feel that a great crime would be committed if the magnitude of the evil we've experienced were just dropped and we let bygones by bygones. We are torn; our moral sense says this evil cannot be ignored and the Word of God says we must forgive".
John Piper - "Future Grace" - IVP, Leicester (1995) - (p265).