Nothing can rock a marriage like the discovery of infidelity. But though an affair can seem like the end of the world, many marriages can and do survive infidelity.

There are many, many reasons people cheat on their spouse, and there are also many, many definitions of “cheating.” Sexual and emotional attraction is a spectrum that ranges from checking someone out as they walk by all the way to sexual intercourse. It’s important for you to understand for yourself what you consider cheating, and to be clear in your own mind what you will do if your partner has an affair.

Don’t spend too much time analyzing why your spouse cheated, if that’s what’s happened. People have affairs for many reasons, and a lot of those reasons are individual reasons of their own that have nothing to do with you. Did you get that? Let me repeat it.

You may be tempted – it’s perfectly normal – to blame yourself for your partner’s cheating. You may feel that you weren’t sexy enough or attentive enough or that you weren’t vigilant enough. But most of the time the reasons have little to do with you. Low self-esteem, as well as psychological problems like alcoholism or drug and sex addiction can lead to infidelity.

So give yourself a break and don’t punish yourself as though your spouse’s affair was somehow your fault.

One very important thing is not to make sudden, rash decisions. Yes, you’re angry and feel hurt and betrayed. But don’t end your marriage instantly in a fit of anger. Don’t make any decisions except to protect yourself and others (if you feel you’re angry enough to hurt yourself or someone else, please get some professional help right away).

Give yourself and your spouse the gift of time and space because absence does makes the heart grow fonder So a separation is advisable, either into different rooms in your home, or perhaps to two different living spaces, for a while.

After a period of separation and silence (I recommend not talking too much during the first angry, unhappy days after something like this comes out) you can start communicating again.Establish a safe, two-way, honest communication with your spouse to brainstorm the problem together. Do not explode like a bomb. An argument is the last thing you want to be doing if you want to save your marriage. If you feel you are still too emotional to talk, then take additional time (and space) off until you begin to calm down and think logically again.

If you want to save your marriage, then here’s what you must do. First, if you are the one who cheated, you need to take responsibility for what you did. Apologize and be sincere about it. An apology that doesn’t use the word “but” is generally best. Don’t qualify it. Don’t blame your partner, even if you feel they drove you to it. Focus on making amends for what you did wrong. End the affair and be clean about it.

If your spouse cheated on you, then be clear with them about how you feel. It’s psychologically healthy to express your frustration, sorrow and anger about what happened. But it’s not psychologically healthy to throw furniture at your spouse or cut yourself or stop eating or express your emotions in damaging ways. Name your emotions, let your spouse hear the pain and reality of the damage, but don’t do more damage yourself. [RELATED: Ways to Improve Your Marriage ]

A word about ultimatums. Don’t.

You know what an ultimatum is – an “or else” type of threat. “If you ever cheat again, I’m going to …” Or, “If you don’t come home this minute, don’t ever come home again!” That sort of thing is very tempting, but it isn’t really useful. If you’ve ever tried it with your kids, you know what I mean. Parents are often tempted to make ultimatums, and they almost never end up keeping them. If you threaten your partner with a nuclear war ultimatum, when the time comes you have limited your own options and forced them into a corner. They are likely to lie and hide anything else that happens if they’re under the pressure of an ultimatum.

Now I’m not saying no consequences. Not at all. But only in your own mind. What I mean is you decide for yourself what your boundaries are and how you will behave if something else happens. “If he ever cheats again, I will move out of the house.” That’s great – it’s really important for you to be clear and honest with yourself about it. But you don’t need to tell that to him. Keep it to yourself. Otherwise it becomes a threat, a weapon used to try and control your spouse, and you and I both know you can’t control another human being very easily.

Time off, whether a couple days, a week, or a month or more, will give you a chance to figure out how you feel and whether you’re willing to try and save your marriage.As always, the only thing you really have control over is yourself and your own decisions. You can decide to punish your partner or to forgive them. That’s up to you. But you can’t figure out what to do right away, so take some time and space.

After that, use the principles I’ve outlined elsewhere about “time share” talking and other safe communication to begin rebuilding your relationship. Open, honest, safe communication will do more than anything else to save your marriage if it can be saved.

Best of luck.