There are two kinds of people who have affairs.  The first are just bad people.  Their self-indulgence and untrustworthiness stems from low character, not a troubled marriage.  If it feels good to them, they'll do it. 

It's a dumb waste of money to spend time in counseling with a serial cheater.  If your spouse has been unfaithful more than once and refuses to be held accountable for their actions, your appointment should not be with a marriage therapist - it should be with a divorce lawyer (and a really good one at that).

The second type of cheater isn't "bad," they simply may be going outside the marriage to have their needs met.  Now, I want to make one thing perfectly clear: I'm not saying that there's any excuse for someone to have an affair. Affairs are bad and there is no justification for breaching your vows.  All I'm doing is giving an explanation for why some people have them.

I can't tell you how many times callers on my show have told the lie, "My spouse's affair came out of nowhere and took me completely by surprise." I say "lie" because after a bit of questioning, they admit about 99.8 percent of the time that there were problems:

"He complained that we weren't having sex."
"She complained that I never listened or helped around the house..."

The bottom line: their spouse wasn't being fed.

Typically, the person who has been cheated on jumps to blame instead of looking at their participation in their spouse's fooling around.  They make it all about how they've been hurt, and ignore the fact that they've betrayed their vows by not supporting or paying attention to their spouse.

If you can understand how you've contributed to a hungry spouse going out to a different restaurant, you can start making the menu better at your home, and the whole thing could be reversed.  Blaming isn't useful - explaining the issue(s) is. 

Knowing whether it was an emotional or physical affair is also important.  The distinction allows you to see what was missing in the marriage.  What was so appealing about that person or situation?  

One of the letters in my book, The Proper Care and Feeding of Husbands, is from a high-paid, ex call girl. In the letter, she explains how most of the married men who came to her were not particularly focused on having sex.  Instead, they wanted to have dates with wine, roses, hugging, talking, and taking baths together.  Why? Because their wives didn't act like their girlfriends.

So, with that in mind, let me give you some suggestions on how to be your husband's girlfriend/wife's boyfriend and affair-proof your marriage:

1. Choose wisely.  If you're dating someone who's spent time going from sexual partner to sexual partner or shacked up before you met them, then their lifestyle is not one of monogamy.  That's one of the many reasons why I advise against people having a lot of sexual partners - it becomes easy to turn to because you're so familiar with it. 

2. Don't ignore your spouse's complaints. Whether it's about housework, money, affection, in-laws, or texting, when your spouse tries to express the reasons for his or her unhappiness, you need to listen.  You don't have to necessarily agree with every point they're bringing up, but you do need to acknowledge their discomfort and do something to improve the situation. 

3. Don't let sex fall off the radar.  Sex is a big part of marriage, and people who are having regular, good sex with each other tend not to get as pissy about the small stuff.  It's amazing what a big eraser great sex is to small annoyances.

4. Wake up every morning, look at your spouse, and think about three things you could do to make them happy they're alive and married to you.  Show appreciation as opposed to having a complaint.

5. Put down the damn cell phone!  Stop texting and talk to your spouse. It's pretty crummy to feel second-fiddle to a smartphone.

6. Talk to your spouse as though you love them. You love this person - so act like it!  Always ask yourself, "Would a person who loved this person behave/talk this way?"

7. Have fun family and marital rituals. Put the kids to bed and watch a movie, take walks, or play a game together.  Just have some fun with each other. 

If you do these things, the chances that one of you will have an affair will be somewhere between zero and none.