Here are half a dozen studies that one could loosely put under the broad umbrella of positive psychology.  Zorba the Greek said "Take what you want and pay for it, says God." and Niemiec et al's study, on the effects of achieving different kinds of goal, supports this statement (for all six research studies mentioned in this blog post see below for abstracts and links).  Quoting Niemiec et al's somewhat awkward language: "The relation of aspiration attainment to psychological health was found to differ as a function of the content of the goals. Attainment of the intrinsic aspirations for personal growth, close relationships, community involvement, and physical health related positively to basic psychological need satisfaction and psychological health.