Men who cheat haven't fallen out of love; they've become unsatisfied with the current state of it. "Cheating usually occurs in the phase of companionate love, when couples begin to settle down, have kids," says clinical psychologist Andra Brosh, PhD. While they're fulfilled in some areas, like being a provider, the romance may be missing.

"We more often think of women complaining about a lack of romance, but men feel it, too," says Dr. Brosh. "They frequently suffer in silence, believing they can't get what they want from their spouses." To avoid this in your marriage, plan nights out together, and discuss hopes and dreams-not just workdays and your son's last soccer game.

Cheaters don't generally pick up random women in bars. "My first husband cheated on me with a childhood friend," says Diane* from New York City. "His family was close to her family, so they never lost touch." Intimacy expert Mary Jo Rapini explains, "A lot of women think that all cheating women are floozies-not true. The relationships are usually friendships first." In fact, more than 60% of affairs start at work, according to Focus on the Family. A good idea: Make sure your husband feels more connected to you than to his business partner. "Spouses go to work, take care of their kids and do separate things at night. That has to stop," says Rapini. She suggests always going to bed at the same time and cuddling.

Fact #3: Men cheat to save their marriages.

"Men love their spouses, but they don't know how to fix their relationship problems, so they go outside their marriages to fill any holes," says licensed marriage and family therapist Susan Mandel, PhD. Then, they can live happily ever after with their wife-and their mistress-without confronting the real issues.