I find that when I think I am asking God to forgive me I am often in reality (unless I watch myself very carefully) asking Him to do something quite different. I am asking Him not to forgive me but to excuse me. But there is all the difference in the world between forgiving and excusing. Forgiveness says “Yes, you have done this thing, but I accept your apology, I will never hold it against you and everything between us two will be exactly as it was before.” But excusing says “I see that you couldn’t help it or didn’t mean it, you weren’t really to blame.”. . .
Real forgiveness means looking steadily at the sin, the sin that is left over without any excuse, after all allowances have been made, and seeing it in all its horror, dirt, meanness and malice, and nevertheless being wholly reconciled to the man who has done it.
In his typical, charming way, Lewis summarizes the essence of forgiveness. I can’t improve on it.