Chances are, you've already had run-ins with your Outer Child -- the self-sabotaging, bungling, and impulsive part of your personality. This misguided, hidden nemesis blows your diet, overspends, and ruins your love life. Your Outer Child acts out and fulfills your legitimate childlike needs and wants in the wrong place, at the wrong time, and in counterproductive ways: It goes for immediate gratification and the quick fix in spite of your best-laid plans.

Now, in a revolutionary rethinking of the link between emotion and behavior, veteran...