Consider somebody who really has it together. The different aspects of her personality seem to complement and harmonize with each other, she is well-liked by nearly everyone, and she is nearly always cheerful and happy. This does not mean that she is shallow—rather, she seems to have access to inner depths that sustain and nurture her. In addition, she is competent and efficient, and she is making excellent progress toward her life goals, with the prospects of an even better life ahead. How are we to understand this person, and to understand how to be more like her? Is it possible to quantify her “state of harmony,” or to predict in advance her high level of functioning? This chapter focuses on these questions, and more generally, on positive personality integration and personal flourishing. What might it mean to say that a person has achieved optimality in personality?