It’s almost a cliché. “But we had a good marriage! Why did he (or she) cheat?” The truth is having a good marriage does not necessarily protect you from the pain of infidelity.

The late Baltimore psychologist Shirley Glass, the author of Not “Just Friends”: Rebuilding Trust and Recovering Your Sanity after Infidelity, found that being happy or unhappy in a marriage often had little to do with sexual straying.

She noted that many people who see themselves as loving and devoted to their partners are still tempted to stray, and that studies suggest that 44 percent of husbands and 25 percent of wives have had sexual relations outside marriage. “Infidelity can occur in any household, not just in situations where partners are promiscuous or rich and powerful. No marriage is immune.”

The workplace is the prime launching pad for modern infidelity. “Today’s workplace is the most fertile breeding ground for affairs. The observed increase in women’s infidelity is because more women are in the workplace and more women are in professions that were previously dominated by men,” Glass wrote.

Many of my colleagues find Glass’ conclusions important because it is so often believed that bad marriages cause affairs. But the truth is affairs cause basically good marriages to turn bad more often than bad marriages cause affairs. Be in the public arena long enough and chances are you’ll meet someone you find attractive. But even having an affair does not necessarily mean you do not love your partner. Curiosity, a craving for adventure, sexual boredom, or a few drinks that lower normal boundaries can get the best of us. We are all vulnerable. The key is avoiding such situations and maintaining clear boundaries.

“It’s not the sex, it’s the deception that destroys a marriage,” Glass concluded. The most difficult challenge after an affair is to heal the trauma of broken trust. As Glass said, “How can you trust anyone again who has looked into your eyes and lied to you?”

Assuming a couple wants to save their marriage, a full accounting of what happened is the best way to begin restoring lost trust. The betrayed spouse has a right to know specifics: How did it start? What happened? Where did it happen? Who knows about it? How much of the “nitty-gritty” gets shared depends on what the betrayed spouse feels the need to know. This may be tough, but the close examination de-energizes the secret infidelity and helps re-establish intimacy in the marriage.

Recovering from infidelity is not easy. One-third of marriages do not survive the affair. Because the work of full disclosure can be painful, it is best done in the safe confines of a therapist’s office with a therapist specially trained to deal with such situations. Therapy usually consists of a combination of sessions with both partners present, plus individual sessions for each spouse. The goal is to rebuild trust and intimacy between the partners, to de-romanticize the infidelity for the involved spouse, and to work through the trauma of broken assumptions experienced by the betrayed spouse.

With commitment, motivation, honest self-reflection, and professional guidance, the marital bond can be restored, and the marriage may emerge even stronger than before the affair.