I find that 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.” If one wasn’t really to blame then there is nothing to forgive. In that sense forgiveness and excusing are almost opposites. Of course, in dozens of cases, either between God and man, or between one man and another, there may be a mixture of the two. Part of what seemed at first to be the sins turns out to be really nobody’s fault and is excused; the bit that is left over is forgiven… But the trouble is that what we call “asking God’s forgiveness” very often really consists in asking God to accept our excuses. What leads us into this mistake is the fact that there usually is some amount of excuse, some “extenuating circumstances”. We are so very anxious to point these out to God (and to ourselves) that we are apt to forget that really important thing; that is, the bit left over, the bit which the excuses don’t cover, the bit which is inexcusable but not, thank God unforgivable. And if we forget this, we shall go away imagining that we have repented and been forgiven when all that has really happened is that we have satisfied ourselves with our own excuses. They may be very bad excuses; we are all too easily satisfied bout ourselves.
From “On Forgiveness” (The Weight of Glory)