What should I do?

[justsadnow]

Hi, I just found out that my partner slept with my friend. It happened over 25 years ago and at the time we were on a break. I feel really shit and I don't know what to do. I love my partner and want to stay with them, but the thought of them together is too much. Obviously the friend is gone from my life and unfortunately I'll probably leave that whole group of friends. I'm so sad, my partner isn't who I thought they were. How can I move on?

Although a long time ago, because you have only just found out, it will have the same effect on you as if he had cheated on you yesterday. You will be questioning your reality and who he really is. It might help you to think about it logically. Has he given you cause for concern over the last 25 years? People change over the course of 25 years. Was it a convenient ONS for him back then while on a break from you? What is it that upsets you? Are you upset because you see it as a sign he wasn't devoted to you?

If they were on an agreed "break" then it wasn't cheating. This can be made as dramatic as you'd like it to be, but the kindest thing to do for yourself is to choose not to. And it is a choice.

You could choose to throw everything up into the air and believe that you have been betrayed, and your DP has changed into a different person overnight, or you can concentrate on everything that you have built with them in the 25 years since, and the valued relationships you have with your group of friends and relegate it back to the past where it belongs, don't let it ruin your future.

The difference for me is that the ex was no longer in any sort of relationship with the OP whereas the friend was.

The ex owed her nothing. The friend owed her loyalty.