People cheat on their partners for many different reasons, most of which you'll never fully know or understand. Many, more than likely, do not understand their own motives for cheating. But whatever the reason, the consequences of an affair are always negative, and the harm it does to a relationship can be irreparable. Know this—whatever their reason for cheating, you are not responsible. Their bad behavior is about them, not about something you did or didn't do to or for them. Your main concern once you find out about the affair is to determine whether or not your relationship can survive the infidelity. Below is a list of some common reasons people have given that will help explain, to some extent, why they cheat on their partners.
Sexual addiction is about people who engage in sexual behaviors that are damaging to them and/or their families. These are hypersexual people who aren't satisfied with one sexual partner. They use sex as a coping mechanism for anxiety, depression, and other life problems; as such, a hypersexual person will be likely to go outside the marriage for sex.
Hypersexual disorder is a term for those who engage in or think about sex through fantasies more than normal.
Those who need to be stroked emotionally and physically due to low self-esteem are likely to seek sex outside a committed relationship because they are a bottomless pit of need. No partner can be expected to keep up with the need these people have to be reassured of their worth.
Cheating for the Sake of Cheating
To these people, it's a game and one they figure they might as well play as long as they can get away with it. This person has no concern for the pain their cheating will cause if they are caught. The thrill of cheating trumps the negative consequences of possibly being found out.
Feeling That “New Love” Feeling
Once the marriage or relationship becomes comfortable, some go looking for the excitement of new love and lust. They want to feel that "new love" feeling again—the one you two felt in the beginning. When they no longer feel it from you, they'll find it in another.
Parental History of Cheating
If someone grew up watching their parents cheat, it's not entirely surprising to see them cheat in their own marriages. Not everyone with a parental history of cheating will become a cheater themselves, however.
If a spouse isn't getting what they want and need from their partner, they find someone to take over their partner's role. Cheating is so much easier than dealing with the problems in their marriage—but that is never an excuse.
Punishing Their Partner
What better way to hurt someone who has hurt you than to replace them intimately? This is a passive-aggressive maneuver, one used by a weak person without the fortitude to confront and solve problems in the relationship.
Sometimes people don’t go out looking for an affair, but get caught up in the moment and before they know it, they are in over their heads. Your partner may not have meant to cheat on you, but simply may have gotten caught up in a moment.