Pushing through the night to study, work, or respond to an emergency can feel downright heroic. You did what you had to do, against the odds. But once the adrenaline wears off and daylight comes, you may suddenly be a little unsteady on your feet. Surviving the day after an all-nighter can be more difficult than it was to stay awake in the first place. A night of sleep deprivation affects your brain -- how quickly you can react, how well you can pay attention, how you sort information or remember it. In fact, studies have shown that after an all-nighter, you may be functioning at a similar level as someone who is legally drunk.

Brace for a Morning Slump You may feel the worst effects just as the next day is beginning. “You would think you would be the most impaired the longer you’re awake, but that is not the case,” says sleep expert David Dinges, PhD, chief of the division of sleep and chronobiology at the University of Pennsylvania and editor of the journal SLEEP. Because of the natural flow of your body clock, or circadian rhythm, “you’re actually at the worst 24 hours after your habitual wake-up time," Dinges says. "You’ll have an unbelievably difficult time staying awake and alert.” That is also the worst time for you to get in a car to drive home. “If you stayed up all night, you should not be driving, period. You are impaired,” says Mark Rosekind, PhD, a fatigue management expert who is now a member of the National Transportation Safety Board. The monotony of the road, combined with your sleep deprivation, can cause you to fall asleep uncontrollably, he says. In a 2005 poll by the National Sleep Foundation, more than a third of adult drivers admitted having nodded off at the wheel.