Why would you ever hold a grudge? What is the point?
It is said that people do not change, but this is not true. Changing is all people do, it is their nature, like shadows cast by a fire on the wall of a cave. They flicker and move, rise and fall.
If you have been wronged and you hold a grudge because you do not wish to let a wrong go unrighted, then you have your work cut out for yourself. There are so many wrongs that go unrighted, in your life and in everyone's that you cannot hope, even at the best, to do more than right the twisting of a single twig in a forest swept by a hurricane.
If you have been wronged and hold a grudge because you do not wish it known that you allow a wrong to go unanswered, you may even succeed, but what would be your victory? That all would know you do not allow a slight to go unanswered, perhaps, yes. But also that all would know that the one thing you care about is you and your image - and what of your image then? That you would consume your whole life - and that image too - to remember and nurse a long-forgotten insult.
Time moves us all, and we move with it. Sometimes people change by letting go of faults, sometimes they change by holding onto them - theirs and others - and being defined by them. But either way they change. We all do, all the time.
Do we change to become more free of slights and insults, more forgiving of others - and in being more forgiving of others, more forgiving of ourselves, and live free until we die free?
Or do we change the other way? By holding on to old wounds and old battles, becoming sterner and harsher with others - and with ourselves also - and live in the sharp and stony embrace of our calcified and ancient agonies, and live imprisoned, and die imprisoned?
Is the person you hated then the same person who exists now? One way or another, no. They have either moved on from such damage, or been further consumed by it, and locked by their own cowardice into a prison of rationalisation and blame far more terrible than any revenge you could ever wreak.
Either way, have a little humility about your capacity for vengeance. Reality is a sterner judge than you, and a fairer one, a kinder one, and a crueler one also, as the circumstances dictate.
Vengeance is mine, says reality.
And while you're holding on to a scorebook from the past, you can never meet the present face-to-face, as it is, as it is now.
Close the book of grudges.