I've written more than enough about forgiveness over the past two weeks, but I do want to emphasize a point or two about the intent of forgiving (I wrote about the object of forgiving here).
Why does a Christian forgive the wrongs done against him? Earlier, I argued the fundamental answer was, "Because Jesus told us to." As with most of my answers, though, that was incomplete. Since Jesus told us to forgive unconditionally, we know it's the right thing to do, but what makes Christian forgiveness the right thing to do is love. We know that to forgive others is to love them.
(And yes, that knowledge can be misunderstood, causing people to forgive what they have no authority to forgive, but I've been over that, too.)
So: Why does a Christian forgive the wrongs done against him? Because he loves the wrongdoers as he loves himself. Because he loves the wrongdoers as Christ loves them.
The thing to note here is that a Christian loves the wrongdoers. That love is what makes the Christian's forgiveness Christian -- or better, Christ-like. Or even Christ's.
So yes, forgiving another person is the only way you'll get over the wrong, and yes, nursing a grudge is spiritual poison, but Christ didn't forgive because it was psychologically and spiritually healthy for Him to forgive. It's not an act of love for another to act out of love for yourself.
It is a smaller thing to wish well or even to do well to one who has done you no evil. It is far greater - a sort of magnificent goodness - to love your enemy, and always to wish him well and, as you can, do well to him who wishes you ill and who does you harm when he can....
Such counsels are for the perfect sons of God. And although all the faithful should strive toward them and through prayer to God and earnest endeavor bring their souls up to this level, still so high a degree of goodness is not possible for so great a multitude as we believe are heard when, in prayer, they say, "Forgive us our debts, as we forgive our debtors." Accordingly, it cannot be doubted that the terms of this pledge are fulfilled if a man, not yet so perfect that he already loves his enemies, still forgives from the heart one who has sinned against him and who now asks his forgiveness.
Those who think we need only forgive those who ask our forgiveness, then, think we are called to be imperfect sons of God.
I've read a lot of comments recently that don't seem to appreciate what it means for Christian forgiveness to be based -- as all things Christian are -- on love. In particular, the "God doesn't forgive unconditionally, so neither should we" sort of argument that I've already looked at betrays a misunderstanding of mercy.
If you love someone, you forgive him the reparation that is due you out of love. Love doesn't wait to be asked before it acts, thank God. As David pointed out in a comment below, love does not seek its own interests, it does not brood over injury. The father of the prodigal son did not forgive his son when he knelt before him; the father had forgiven the son long before, or else he would not have been watching for his return. In fact, there's no suggestion there was ever a point in time when the father hadn't forgiven his son. That's perfect love.
And that, it seems to me, is God's love for us. "God doesn't forgive unconditionally" is, in fact, a false statement. He does forgive, He has forgiven us all we have done wrong and all we will do wrong. He does not seek His own interests, He does not brood over injury.
Indeed, we cannot harm God's interests, we cannot injure Him. What our sins do is harm and injure ourselves and each other. These injuries God does not repair instantly, because that would be contrary to His will for us as free beings.
As all good Catholics know, there are temporal punishments due our sins even after we are given sacramental absolution. But the punishment due us, as I've tried to show below, is a different matter than the reparation due God. This reparation is something God forgives, not because of anything we do, but because God is love.
The perfect sons of God forgive even as they are offended, just as their Father does. Few of us are perfect; all of us can pray for the graces we need to be better today than we were yesterday.