Despite our romantic images of suffering geniuses who have enriched our civilization, creative by day and tormented by night, there is a growing body of evidence that people think more creatively and expansively when they’re happy than when they’re not.

Happy people are more energetic and physically healthier than those who are not. And happiness adds about nine years to life expectancy. So even if you don’t think that happiness is such a big deal in itself, it seems to serve a useful instrumental function. Happy people are more likely than unhappy ones to change the world in positive ways.

The Paradox of Choice by Barry Schwartz