Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you.
Merriam Webster defines "forgive" as follows:
to cease to feel resentment against (an offender)
Forgiveness does not imply pretending the offense never happened; for that we need forgetfulness.
Forgiveness does not even suggest the offense does not matter. Forgiveness merely means one chooses not to be angry.
Why must we forgive? Why should we not be angry at those who wrong us?
Forgive Because We Are Forgiven
The immediate answer lies in the verse above: We should forgive because we ourselves have been forgiven. We should do for others that which we desire for ourselves—to fail in this is to become an hypocrite. If we seek forgiveness of our sins, any failure to forgive the sins of others becomes therefore an additional sin added to our tally.
For our own sake we must forgive.
Moreover, anger hurts. Anger is painful. Anger precludes happiness. When has any man truly enjoyed his moments of anger? Setting aside anger is necessary if we are to ever enjoy happiness.
For our own sake we must forgive.
Forgive, But Never Forget
We must forgive, but we should never forget. When we forget we open ourselves to the same mistakes, the same foolish trusts, the same careless actions, that allowed offense to happen.
Also, if we forget the wrong done to us, we can never truly choose to put aside the anger arising from the wrong. Instead, by forgetting we are choosing to ignore the anger along with the wrong. Where there is forgetfulness there can never be forgiveness.
For our own sake we must forgive. For our own sake we must never forget.
Seek Justice
Yet surely this leads to a dilemma: without anger, how are we to confront those who wrong us? If we put aside righteous indignation, and thus put aside the anger-driven quests for revenge, what is left for us to seek? What remains for us to do?
The answer for this lies in understanding another word—"justice":
the maintenance or administration of what is just especially by the impartial adjustment of conflicting claims or the assignment of merited rewards or punishments
That which is just is that which is grounded in fact and reason. That which is just is necessarily predicated on reality—on what is.
Facts and reason—empirical reality—are what remain to us when we set aside anger and emotion, and it is through fact and reason that we extrapolate and appreciate the consequences attendant upon every action, right or wrong, good or bad.
By laying aside anger, and the vengeful impulses which follow, we are left with a simple quest for justice. We are left with the simple adjudication of consequences for all that happens.
Forgiveness is therefore the essential prerequisite to justice. Until we forego the impulse for revenge, motivated by perception of what should be rather than what is, we cannot seek justice. We cannot be driven both by notions of what should be and appreciation of what is.
If we are to have justice, we must practice forgiveness—for our own sake, and for the sake of us all.
Forgiveness is, in the final analysis, justice for the sake of us all.