You're right - my comment was a little too global, and exceptions certainly exist. There are those people who, for example, may have an illness that causes them to lose all sense of right and wrong, such as someone who is a sociopath in the clinical sense, i.e. "a pervasive pattern of disregard for and violation of the rights of others and inability or unwillingness to conform to what are considered to be the norms of society".

But that's extremely rare, Lenny. Nearly every other factor - alcoholism, addiction, many mental illnesses, abusive upbringing, etc. - may push a person towards committing adultery, but that person is still able to choose a different path. Because of these factors, that choice may be enormously difficult... but it's still a choice, sometimes selfish, sometimes not.

Maybe, instead of saying people cheat because they feel like it, it's more accurate to say that most people commit adultery because they choose to stop battling their urges.