Wait three days to call after the first date. Don't sleep together too soon. Encyclopedias have been devoted to "The Relationship Rules" and "Dump his ass!" is the cardinal rule of cheating, as if the love life you've built together is a game of Monopoly and he's been pilfering that tiny, fake money. If you've been scorned, hell hath no fury like you, but should your snap reaction be to throw it away just because "that's the rule?"
Maybe you should. But then maybe you shouldn't. The point is, these rules of attraction don't give you a choice. And what many don't realize, especially when it comes to infidelity, is that you've got one. It's just not easy to make.
First, determine if you want to continue the relationship. There are certain circumstances that are almost irreversible nails in your love coffin: if she cheated with your sibling/best friend/mom. If the cheating is chronic versus a one-time mistake and she just blew chance #8.
If he's in love with the person he cheated with, chances are it won't resolve itself. Or if he had to put a lot of work into cheating on you, like continuously lying and flaking out on other relationship commitments, like picking up the kids in order to cheat. In these cases, do not pass "Go" and do not collect $200.
Similarly, the decision to work through cheating should never feel like rolling over and taking it, nor should it be for the kids or money, nor out of obligation or fear.
If the straying moment was a one-time mistake, or even a slightly prolonged mistake, you might still make it. But only if you both genuinely want to, because it won't be easy. If you do decide to trudge through the layers of post-infidelity crap dumped on your relationship, here's some advice.
Cheater, why did you cheat? Is your partner more married to their work than you? Or is it a poisonous resentment stemming from deeper issues? The first question is, is the root of your cheating something that can actually be fixed?
Lover scorned, break some dishes and then calm down and get your tough questions answered. Any question asked should be answered honestly by your partner, since, Ms. Cheater, withholding from your partner "to protect her" actually just protects your yellow-bellied self from dealing with your actions.
Don't make excuses. Extreme drunkness is not a "Get Out of Jail Free" card. Own your mistakes. Lover scorned, show some compassion and don't continuously use "that time" as ammo. If you can't both forgive and forget, forget it.
Poor little cheater has the difficult job of regaining your trust. If you don't trust that he/she truly wants to put in the work to be with you, then call it quits. Because if you don't have this scrap of trust left, then there's no trust at all and without trust, there's no relationship.
Take "it" slow. This is one thing angry make-up sex can't fix. Trust first, intimacy second.
Seek professional counseling!
Rehash your relationship boundaries and make sure that they work for both of you. Run new terms on a trial basis or take a break to regain your relationship's composure. (During this break, do not sleep with the person you cheated with, idiot.)
I highly recommend reading Tristan Taormino's Opening Up during this rebuilding time. While the rate of infidelity and our straying human nature make a great case for non-monogamous, "open" relationships, that's a whole other column, and besides, whether you're open or monogamous, the terms of your relationship can still be violated or "cheated" on. No matter your relationship style, Opening Up offers interesting insight into our views of infidelity and how it affects our relationships and teaches all kinds of couples how to deal with painful emotions and establish healthy boundaries.
Most importantly, ask yourselves "Is it worth it?" Was cheating worth the sacrifice of your entire relationship? Is your relationship worth the struggle to rebuild? If you both want it to be, cheating can be a bad moment in the complex web of your relationship, but it doesn't need to be the defining moment. What's it worth?