how do you forget something like a guy having sex with your girl?

Simple although you may not agree. Hopefully your relationship is based on friendship and a host of factors that are not sex. If so then consider why sex is the cornerstone deal breaker. You don't own or control the other person so you have to decide what is important for you. Sex is generally a shot term gratification which while can add to a relationship shouldn't define it. Now Hopefully your situation is based on trust, honesty and a lot of other factors that make infidelity a minor problem. Also, there is a big difference between a physical attraction and an emotional one. One is fleeting. If you have a hard time separating the two then you probably can't move past it but if you value the relationship as a whole you should be able to. Everyone is different though.

/r/TooAfraidToAsk Thread