Affairs often involve a lack of self control. People give into urges or fantasies that they have been keeping active in their minds. The whole affair situation worsens when a spouse attempts diminishing what happened with the excuse that they were drunk (or stoned). Such an admission suggests that there are substance abuse problems in addition to the poor self control related to the affair. Disorders of self control often happen in combination like that. One self control problem has a way of spilling over into another area of their lives. If you or your spouse has such multiple self-control problems, (over eating, purging, gambling addictions, drug addictions, drinking problems, spending addictions, etc.) you need professional help. Many people make the mistake of saying they are getting better when all they are doing is switching the self-control problem from one area of their lives to another.
The only exception I have seen regarding the self-control issue (where the person acts out their fantasy or urge) is related to affairs involving sexual addicitions, although that in itself is a self-control disorder as well. Some sexual addicts have affairs due to being driven to do so. It is almost as if their brain goes on automatic pilot and they are then driven to act out.
