Sleep is the natural state of bodily rest. When you sleep, your body rests and restores its energy levels. Consistently good sleep helps you cope with stress, solve problems and recover from illness, and helps ensure long-term physical and mental well-being. * Infants require about 16 hours a day *Teenagers need about 9 hours on average * Most adults need 7 to 8 hours a night for the best amount of sleep, although some people may need as few as 5 hours or as many as 10 hours of sleep each day *Women in the first 3 months of pregnancy often need several more hours of sleep than usual