The thing about being forgiven for anything is that for it to have any affect on the one that is forgiven, the forgiveness must be accepted.

If you look at the song you quoted above, it points out a very important piece of what it means to be forgiven by God. It isn't that He simply forgives our debt, but rather that He PAID our debt in full Himself and credited it to our account.

We were in bondage to our sins and what we had not just become but what we had really been all along. We were being held captive by our human nature and doing what WE believed we had the right and entitlement to do. He did not just agree to let those things slide, but rather paid the ransom so that we might be set free from those very things that prevented us from obeying Him.

True repentance does not merely imply a change in the way we act. It isn't just no longer doing the things we once did but coming to an understanding that the things we did were not justified by anything we might have attributed them to or to them. Real repentance is a change in the way we think and it is the change in our thinking that leads us to act differently.

So if we have truly been forgiven by God, we haven't just had our debts wiped clean; that debt has been paid in full, just not by us. The ledger now has as it's only entry the payment made on our behalf by the one to whom we owed the real debt to begin with. We don't just begin with a clean slate but with a clean nature as well.

Forgiveness by other people takes longer at times because they are under no obligation to cancel the debt we owe them. This is why Dr Harley talks of Just Compensation and not just unmerited forgiveness in cases of betrayal. It becomes up to us to supply the payment our spouse needs from us so that our debt might be paid in full. If they choose to vanquish any part of the debt it is entirely their choice and until they wipe the books clean it is up to us to continue paying the debt off until it can be credited as paid in full. Once the forgiveness is offered, it still remains up to us to accept it before it has any real affect on us.

As long as the one we wronged is willing to accept our payments, it means we can continue to pay down the debt until they either forgive the remainder or we know the debt has been paid entirely. Considering our vows of faithfulness until death, that gives us a long time to work off the debt we owe.