Ever since Adam and Eve ate the apple, Ulysses had himself tied to the mast, the grasshopper sang while the ant stored food and St. Augustine prayed “Lord make me chaste — but not yet,” individuals have struggled with self-control. In today’s world this virtue is all the more vital, because now that we have largely tamed the scourges of nature, most of our troubles are self-inflicted. We eat, drink, smoke and gamble too much, max out our credit cards, fall into dangerous liaisons and become addicted to heroin, cocaine and e-mail.

Nonetheless, the very idea of self-­control has acquired a musty Victorian odor. The Google Books Ngram Viewer shows that the phrase rose in popularity through the 19th century but began to free fall around 1920 and cratered in the 1960s, the era of doing your own thing, letting it all hang out and taking a walk on the wild side. Your problem was no longer that you were profligate or dissolute, but that you were uptight, repressed, neurotic, obsessive-compulsive or fixated at the anal stage of psychosexual development.

Then a remarkable finding came to light. In experiments beginning in the late 1960s, the psychologist Walter Mischel tormented preschoolers with the agonizing choice of one marshmallow now or two marshmallows 15 minutes from now. When he followed up decades later, he found that the 4-year-olds who waited for two marshmallows turned into adults who were better adjusted, were less likely to abuse drugs, had higher self-esteem, had better relationships, were better at handling stress, obtained higher degrees and earned more money.

What is this mysterious thing called self-control? When we fight an urge, it feels like a strenuous effort, as if there were a homunculus in the head that physically impinged on a persistent antagonist. We speak of exerting willpower, of forcing ourselves to go to work, of restraining ourselves and of controlling our temper, as if it were an unruly dog. In recent years the psychologist Roy F. Baumeister has shown that the force metaphor has a kernel of neurobiological reality. In “Willpower,” he has teamed up with the irreverent New York Times science columnist John Tierney to explain this ingenious research and show how it can enhance our lives.