Psychology professor Shawn Achor’s The Happiness Advantage: The Seven Principles of Positive Psychology That Fuel Success and Performance at Work is something of a revelation. In a nutshell, Achor says that our model of success in America is completely backwards--we think that meeting goal markers in our careers will make us happy, however, when we reach these supposedly happiness-inducing milestones, we still aren't happy. Instead, we make new goals that will make us happy.  In this way, happiness is outside of the horizon.  Instead, Achor posits that happiness is what gives people an advantage in business and that happiness is a personal decision and is not so completely affected by external stimula.  His message is liberating.