The bills come in the mail every month, asking to be paid on time. (Somebody who used to have my telephone number owes somebody something -- the collections companies keep calling me, looking for him. Sorry, wrong number!)
But there's one debt you'll never have to worry about. It's been paid in full, before you were ever born. In fact, it was paid in full before the stars began burning or this Earth was set spinning in the blackness of space.
That's the debt of your sins. It's already been paid. Before you were born, before the universe was created out of exactly nothing, God had a plan in place to unite the whole universe to himself by one selfless act. The eternal Son of God was made flesh, and in his flesh reconciled all of us -- united the physical creation with its Maker, through and including the resolution of all sin for all time. See Revelation 13:8, John 10:11, John 12:32, Eph 1:3-8, and many other scriptures.
One more: John 19:30 says: 'After Jesus drank the wine, he said, "Everything is done!" He bowed his head and died.' The Greek word for "everything is done" is 'tetelestai' which is a term found on business documents of that time period, to note that a debt was paid or a transaction completed.
It's all done. You can't do anything to pay for your sins or to present yourself clean before God, because he arranged it all, even before you had sinned once. Your repentence doesn't change the truth -- it simply means you've turned around and recognized what is already true. So when the Accuser calls you to hound you about your guilt, you can just hang up. It's already been handled!