Hands Clean
Walk away with clean hands. That's what I tell them as they leave my office. Their partner has been cheating. They want revenge. They're hurt, pissed off and confused at the same time. It's not a fun place to be in. Do everything you can to stay honorable. Don't call the person they cheated with. Even if they knew your partner was in a relationship, it has nothing to do with them. I know many would argue differently, but if someone can steal your partner, they were never really totally invested in you in the first place. Take the loss, but don't lose the lesson
People cheat for a variety of reasons. None of them good. And yes, relationships can bounce back after an infidelity. But its going to take some work. Whatever amount of work you're thinking, now I want you to double that. But I like the hands clean approach. If you stay with you're partner, the infidelity should not be used as a life long kick to their head, any time any issue pops up. Infidelity usually happens because of a lack of honesty. If you're needs were not being met, or if you were attracted to another person, a conversation should take place. I'm not talking about seeing an attractive person and pointing it out to your partner. I am talking about your insecurities in the relationship, that is having you think that stepping out may be a viable option.
Do you know why the "high road" is lonely at the top? Because so few are willing to put the work in. BUT... once you get there, you have a clear line of sight. You see everything better. Which means the likelihood of you getting lost again is slim.
Hands clean. Make it a way of life. And life will make a way for you.