Remember the Duck
This story told by my friend and former professor, Steve Brown, illustrates well the radical discrepancy between the ways in which we hold other people hostage in their sin and the unconditional forgiveness that God offers to us in Christ.
Do you remember the story about the little boy who killed his grandmother's pet duck? He accidentally hit the duck with a rock from his slingshot. The boy didn't think anybody saw the foul deed, so he buried the duck in the backyard and didn't tell a soul.
Later, the boy found out that his sister had seen it all. Not only that, she now had the leverage of his secret and used it. Whenever it was the sister's turn to wash the dishes, take out the garbage or wash the car, she would whisper in his ear, "Remember the duck." And then the little boy would do what his sister should have done.
There is always a limit to that sort of thing. Finally, he couldn't take it anymore–he'd had it! The boy went to his grandmother and, with great fear, confessed what he had done. To his surprise, she hugged him and thanked him. She said, "I was standing at the kitchen sink and saw the whole thing. I forgave you then. I was just wondering when you were going to get tired of your sister's blackmail and come to me."
If he already saw and forgave you, don't let anybody say to you, "Remember the duck."
Paul writes in 2 Corinthians 5:19, "God was reconciling the world to himself in Christ, not counting people's sins against them." The good news of the gospel is that, for all of us who trust in the finished work of Jesus, God does not count our sins against us–he counts our sins against Christ!
Our own failure to grasp the gospel shows itself when we demand penance from those who have wronged us. Whatever offense I've received is infinitely smaller than the offense God has received from me. And since God has freely, fully, and unconditionally forgiven us in Christ (counting our sins against him) we should be quick and desirous to freely, fully, and unconditionally forgive.
There's simply no better way to get people to contemplate God's unfathomable love and grace than by granting them what he's already granted.