Pride and ego can make both choices difficult for a lot of people.
However it is said that we (forgive) for ourselves. The act of forgiveness frees us from dwelling on the hurt that was caused. You can choose to forgive someone and decide to no longer associate with them.
A creditor can (forgive a loan) meaning they are no longer going to pursue getting the money back from you but they will not be extending you any new credit.
Personally speaking I believe coming clean and admitting you were wrong and truly feel bad about your actions is probably the most difficult. Afterwards you have no control over how the other person will react. This causes you to feel uneasy after the admission.
Not every mistake is a "mistake". Forgetting to dot an (i) or cross a (t) is a mistake or making a right turn when you meant to turn left, forgetting to bring something to an event ....(these are all mistakes).
Breaking a promise, cheating, lying, or misleading someone are "deliberate" actions one (knowingly) chose to do.
A "mistake" in my opinion is (unintentional).