"If I let it go, they get away with it"

Think again about the deposit, eight years on. The person in that example could tell you the amount, the month, and what their mother said on the phone. Keeping hold of those details feels close to a duty. If they stopped being angry, it would seem as though they'd agreed it was fine. The grievance can feel like the only remaining record that a wrong was done.

Wanting wrongs to count is a good instinct. A society where nobody minded being cheated would be a bad one to live in, and I wouldn't want to talk anybody out of minding.

Now look at what holding on does to the other person. The ex has no idea how you spent Tuesday evening. The parents don't know that Christmas is hard work for you, or if they sense it, they don't know why. None of it reaches them. You're the one serving the sentence.

I think two things have got tangled together, and they come apart quite easily. One is holding someone to account. The other is carrying what they did around with you.

Holding someone to account happens outside your head, and it's aimed at the person or at some authority over them. You tell them plainly what they did and what it cost you. You make a formal complaint, use the small claims court, go to the police or see a solicitor. You end contact, or you warn other people where that's fair and safe. Each of these has a start and a finish, and afterwards something in the world is different.

Carrying happens inside your head, and it has neither a start nor a finish. My observation is that people who carry the most have often done the least holding to account. That makes sense, because holding to account is frightening and carrying is familiar. The parents have never been told. The manager has never been asked.

So the first question for an old grievance is whether there's a way of holding them to account that you haven't tried. If there is, that may well be your next move. It will serve justice better than another year of carrying would.

Sometimes nothing of that kind is possible any more. The time limit has passed, or the person has died, or there's no evidence, or confronting them wouldn't be safe. That's a hard place to be. But carrying doesn't do the job that those measures would have done. It changes nothing for them, and all the cost falls on you.

You may be expecting me to tell you to forgive. I'm not going to. It's your business, and the research gives a reason for care. Laura Luchies and her colleagues ran four studies, one of which followed 72 newly married couples for five years. People who forgave a partner who made amends and treated them well gained self-respect. For people who forgave a partner who didn't, self-respect went down. The authors called this the doormat effect. If the person who wronged you isn't sorry and is still doing it, forgiving them may cost you something.

There's evidence on the other side too. Nathaniel Wade and colleagues pooled 54 studies in which people were taken through structured forgiveness work, usually with a therapist or in a guided group. Those people ended up more forgiving, and also less depressed and anxious, than people who got no help. Longer programmes did better. So forgiveness can be good for the person doing it. It's slow work, and whether it's wise depends partly on how the other person has behaved.

What I'm asking for is narrower than forgiveness. Stop making your next move depend on theirs. You don't have to like them, see them, excuse what they did or tell anyone it's all right now. You only have to stop waiting for them before you get on with your own life.

The objection is that then there'd be no record. So make one. Write down what was done, when, and what it cost you, in plain words, and keep it somewhere safe. A fact on paper stays true without being rehearsed every day. Some people find that once it's written, the urge to keep going over it gets weaker. I can't promise that.

One last exercise, about apologies. Work out how long you've been waiting for this one. Ask yourself honestly how likely it is to come. Then picture the day after it arrives, and ask what you'd do differently that day. Whatever that is, consider whether you could do it without the apology. In most cases I think you could.