I'd always been fascinated by the trope of the doppelgänger and its long literary life, from Dostoyevsky to Nabokov to Spider-Man. Often, in books, these physical doubles represent the worst a character is capable of. Lately, though, perhaps because at age 41 I'd begun feeling less like the captain of my life and more like its deckhand, I'd started wondering if there was someone out there who embodies not your worst self, but your freest one—a person who encapsulates everything you've ever dreamed of becoming. Let's call him your Cooler Self. All those dreams that got lost along the way, the ones that were casualties of chance or duty or cowardice: There's a "you" out there—a mountain climber or war photographer or race-car driver—who brought them to fruition.