Based on his work with Dr. Len Ochs' "Flexyx" Neurotherapy, now amounting to thousands of hours of treatments for a variety of disorders--and for optimal performance candidates--including the author himself and colleagues, Stephen Larsen develops a coherent theory which shows how human responses can vary from rigidity and stereotypic behaviors, to flexibility, metacognition and mindfulness. Depression and anxiety both are examined as functional distortions, and a model of mental/emotional health through flexibility developed.