Every so often, you meet people who radiate joy—who seem to know why they were put on this earth, who glow with a kind of inner light. Life, for these people, has often followed what we might think of as a two-mountain shape. They get out of school, they start a career, and they begin climbing the mountain they thought they were meant to climb. Their goals on this first mountain are the ones our culture endorses: to be a success, to make your mark,...