Every once in a while, re-check a grudge. Some of them are just your pride keeping a file open.

Resentments rarely get reviewed. They are filed while the hurt is fresh and then carried unexamined, so the version you hold was written on the worst day, by the most wounded version of you. Some would still stand up today, and some are being maintained by nothing more than not wanting to have been wrong.

Take one and look at it properly. Ask what actually happened, what it cost, and whether the person you are now would have filed it at all. If it holds, fine. If it does not, you can simply stop carrying it.