Hume describes his own “open, social, and cheerful humour” as “a turn of mind which it is more happy to possess, than to be born to an estate of ten thousand a year.” Why does he value a cheerful character so highly? I argue that, for Hume, cheerfulness has two aspects—one manifests as mirth in social situations, and the other as steadfastness against life’s misfortunes. This second aspect is of special interest to Hume in that it safeguards the other virtues. And its connection with the first aspect helps explain how it differs from Stoic tranquility. For Hume, I argue, philosophy has a modest role in promoting human happiness by preserving cheerfulness.