For most folks, emotional and sexual cheating is like taking an addictive drug most often without even knowing it! I call it taking the "affair pill".
Over half of all married men and woman cheat sexually, despite significantly increased conservative values to the contrary. If fact, marital infidelity rates have more than doubled over the last 40 years.
As I've always told my clients, the best way to avoid cheating is to simply define it properly. Like crack cocaine there are short term pay offs for the user. The brain chemistry is actually very similar between cheating and using crack.
I've written a detailed and highly popular Hub recently, called: Why Defining an Affair is Its Best Definition.
For serious offending partners I would add that they take a relapse prevention approach to stopping their cheating behavior. For example, identifying high risk situations for cheating (online, at work etc in keeping with recent relationship science).
I advise that most couples need to develop a safety plan for what they will do instead, how they will cope with their high risk situations and as I said in my Hub - getting to their real partner fast instead of the affair partner, at those times.