Admittedly, the messenger quoted above is Shakespeare’s arch-villain Iago. But when the message is right, it’s right. Neuroscience and psychology have identified willpower, largely a co-production of genetics and early childhood training, as essential to success in school and beyond. And while overall levels of willpower vary from person to person, there’s only so much of it any of us can expend over a given time period; like a battery, willpower gets depleted, and needs time to recharge. We tend to think of willpower as the drive to achieve. The more of it you have, the more productive you can be. That’s accurate, says Princeton neuroscientist Sam Wang, co-author of Welcome to Your Brain, but it’s a little more complicated than that. Willpower, as neuroscience understands it, is mainly a matter of self-restraint,or effortful self-control.At the most basic level, it’s the ability to resist a slice of quadruple chocolate mousse cake with buttercream frosting, or to avoid quitting in the middle of a tiring workout. The better able you are to resist your own natural impulses, the more effectively you can focus your mental energy on the task at hand, however pleasant or irritating it may be. The net result: getting more things done, and doing each thing better. Because no matter how cool your job is, no matter how much fun your friends are, no matter how cushy your financial reserves, life demands discipline. Willpower is Like a Muscle . . . it can be developed through exercise, and exhausted through overwork. The preschool years, up to about age 6, are a crucial period for developing willpower. While Tiger Motheringmay actually cause counterproductive stress in developing brains, structured play, second language learning, and music lessons have all been shown to help children build this essential habit of mind. So what if you’re an adult whose parents allowed you to run amok, feasting on ice cream sundaes at will?