“Quality sleep impacts performance profoundly,” says Christopher Winter, a neurologist and sleep consultant to many professional sports teams, including the San Francisco Giants and the Oklahoma City Thunder. Frequent travel across time zones turns their players into what Winter calls “glorified, overpaid shift workers” who are particularly vulnerable to the repercussions of being chronically tired. Winter studied Major League Baseball players and found that 86 percent of those who reported the highest levels of drowsiness were no longer in the league two years later.

Everyone, whether hulking offensive linemen or third graders, needs a set wake-­up time, Winter says. That time will depend in part on the proclivities of your circadian clock, or what scientists call your chronotype (are you a morning person or a night owl?). To figure out how much sleep you need to feel alert, work backward from that wake-­up to find a suitable bedtime.

Winter tells athletes to make their bedrooms so lightproof that they have “trouble finding the doorknob” in the middle of the day. (Eye masks can help create darkness on planes or in hotel rooms.) All light disrupts sleep, but the blue wavelengths, the kind emitted by electronics like TVs and smartphones, tells a part of our brain called the suprachiasmatic nucleus to suppress the release of melatonin, a hormone associated with the onset of night and drowsiness. “No screens in the bedroom,” Winter says.

But sleeping better is not just about those presleep moments, the “falling” part. It requires a certain degree of daylong mental and physical discipline. Above all, beware the psychology of insomnia, which Winter describes as a self-­perception problem of this sort: “Ed from accounting is the tall guy, Joanne is the cute girl, and I’m the one who does not sleep.” Sleep is not a bus stop; if your 10 p.m. bedtime passes by and you’re still awake, don’t fret. Trust that sleep — an innate physiological need, like hunger and thirst — will come. No one, especially children, should be given the impression that they are “bad sleepers,” Winter says.