Although people pursue life outcomes because they believe that these outcomes will make them happy, research shows that external life circumstances have a surprisingly small effect on happiness and subjective well-being. In contrast, personality traits and other stable factors appear to play a more important role in happiness. Happiness is heritable, stable over time, and moderately to strongly associated with personality characteristics. Empirical support for these conclusions is reviewed, and more recent evidence that challenges strong interpretations of personality effects is discussed. Although the effects of personality are robust, long-term levels of happiness can and do change.