I forgive myself.

There is a library book somewhere that never went back. The branch closed years ago, the card system was replaced twice, nobody on earth is looking for it — and the fine has gone on quietly accruing in one person's head for two decades.

Most private guilt works like that. The debt was settled long ago, or was never really owed in the first place, and the payments continue out of habit at three in the morning.

Forgiving yourself is not a ceremony and it does not require the other party. It is mostly the decision to stop paying interest on something already closed.