To meet unrestrained anger in any human being is in itself always very shocking. I think the effect may be partly physical. Have you noticed how one angry man bursts out (say, in a crowded ‘bus) and a tension comes over everyone? Indeed one nearly becomes equally angry oneself. When one gets this shock along with injustice, of course there is a compound reaction.
It is at first sight so easy to forgive (especially when one knows that the anger was pathological) but then one sort of wakes up five minutes later and finds one hasn’t really forgiven at all–the resentment is still tingling through one’s veins. And how one has to watch that ‘feeling hurt’–so seldom (as one would like to believe) mere sorrow, so nearly always mixed with wounded pride, self-justification, fright, even (hiding in the corners) desire for retaliation.
– C.S. Lewis to Mary Willis Shelburne, 21 May 1956; cited in Yours, Jack: Spiritual Direction from C.S. Lewis (HarperOne, 2008), 291
Lewis here again demonstrates how perceptive he is.
Forgiveness is necessary partly because the real hurt and injustice is almost always mixed with less noble elements, which seem to spring up unawares.
He also notes well how forgiveness can be a process—one puts a matter aside, only to wake up with the recognition that it is back again.
Like all such weaknesses, we can only keep evicting our unwelcome visitor, and pray God to take it from us. But, we should not be surprised—or perhaps, terribly worried—when the temptation to not forgive recurs like any other temptation does.
At times, perhaps it is best to “keep a place in [our] heart[s] for forgiveness, and when it comes, welcome it in.”