Dealing with a cheater is pretty simple. If he can’t be bothered not to stick his dick into some other girl, then he can be replaced. You’re the prize, remember? Cheating is the ultimate betrayal and despite attempts at excuse or justification, there’s never any excuse or justification. It doesn’t matter if he told you immediately after. It doesn’t matter if it was just one time. It doesn’t matter if it was after you were exclusive but before he was officially your boyfriend. When it comes to cheating, don’t be a fucking idiot.
If a person agrees to be in a monogamous relationship with someone else, then the very least those people can do is uphold the one major stipulation of a monogamous relationship.
If you value yourself highly, then don’t put up with people who do hurtful things to you, and cheating on someone is the most clear-cut, absolute violation of that agreement. How could you ever trust someone who would do something that is guaranteed to cause you an immense amount of pain?
But Betches, you might proclaim, everyone makes mistakes! Don’t we all deserve a second chance?! No, Carmela Soprano, we don’t. The kind of guy who would cheat, and especially the kind of guy who would cheat on YOU, doesn’t respect you enough to not inflict conscious levels of pain on you and therefore he has G2G. Maybe he’ll learn his lesson after you break up with him and maybe he won’t, but either way it won’t be your problem. The higher the regard you hold yourself in, the less disrespect you put up with from a shitty boyfriend. So no, you’re not going to meet him on the Brooklyn Bridge and decide to forgive and forget like some delusional Sex and the City character. You’re going to put on “Should’ve Said No,” dump his ass, and send the clear message that there are some girls too great to give out second chances like they’re Fairway coupons.
Occasionally you’ll run into a bro who will give you a rant about how “unrealistic” monogamy is. If you’re casually seeing or fucking someone with this opinion, it’s time to run. Then again, at least this guy is being up front about his decision to not want to be exclusive with you. But, at heart, every guy who claims that there’s “a biological imperative to spread his seed,” really means that he doesn’t think that you are worthy enough to be exclusive. As someone who knows she’s the prize, you’re obviously going to move on from this situation immediately for someone who is dying to lock you down, not negotiate terms and conditions to spout bullshit “evolutionary theory” about why men “aren’t built for commitment.”
Worse is the guy who tries to use this excuse after he has cheated on you. If you believe that people aren’t meant to be monogamous, that’s fine. Hell, maybe they’re not. But if that’s your belief, then just do what the above guy did, and be up front. Don’t pretend you’re into monogamy and then make a bullshit excuse about it afterward. That’s called being a liar, and not even owning up to your shitty, weak actions, a.k.a. the worst kind of cheater.