He thought forgiveness ought to be like a cancelled note, torn in two, burned up so that it could never be shown against anyone again. You might still retain a memory of it, but you would never use it as a threat. Like something erased on a computer, the memory is there, but the access to it is gone.
Jesus was very specific about forgiveness. He said we will be forgiven with the same measure we forgive. Paul urged us to be tenderhearted, forgiving one another, as God for Christ's sake has forgiven us. When God forgives, he's not going to go back and bring it up again.
There is nothing quite as fresh as the full feeling of forgiveness — both when that forgiveness is received and also when it is shared. Let's not carry any of the old junk into the New Year. Let's forgive and let the past be gone!
For if you forgive men their trespasses, your heavenly Father also will forgive you; but if you do not forgive men their trespasses, neither will your Father forgive your trespasses (Matthew 6:14-15 RSV).