15 Lessons Movies Can Teach Us About Cheating

Lesson: Beware the rationalization that it's "meaningless sex."

Diana (Demi Moore) and David (Woody Harrelson) are a happily married couple in desperate need of cash. When a rich, handsome man with a great head of hair (Robert Redford) offers them $1 million for one night with Diana, they tell themselves it's OK because the sex won't mean anything. But even after the deed is done, David's jealousy continues to eat away at him and the marriage.