Why Do People Have Affairs?

The first question most people ask when they learn of their partner's affair is, "Why?" And the answers they come up with are usually based on personal blame. They blame themselves, their partner, their relationship, or the third party. They see it strictly as a personal problem, a personal failure of the people involved. This is a very simple explanation for a very complex question.
Usually there are three different kinds of forces that are working together:
Forces within the individual that pull them toward affairsForces within the individual that push them toward affairsSocietal factors