The field of positive psychology has produced an avalanche of new research. Exactly what have we learned in the past fifteen years? First, that happiness is available. Our level of happiness (much like our brains and nerve pathways) is far more malleable than we thought. We are not so hardwired—by genetics, upbringing, or past experience—to a fixed range of mood state as science insisted was the case just twenty years ago. What’s more, the factors that can make us significantly and lastingly happier are not the big things we might expect would make the difference, but the little things we so easily overlook.