A grudge feels free. It charges you in years.

Holding on to a wrong seems costless, because the other person is not paying anything for it. The expense is quieter than that, in attention rented out to somebody you do not like, in a relationship that could have continued, in the evening you spent rehearsing the argument again. None of it shows up on a bill.

Work out what one grudge has actually cost you in time and mood. Letting go is not deciding the thing was fine or that the other person was right. It is declining to keep paying for something that already happened.