Okay, okay, so I’m a Monkees fan. I like Saturday because I generally get to sleep past 5:36 a.m. and that extra four or five hours feels good.
This is from Women’s Health at the New York Times site.
While the average adult needs eight to nine 
hours of sleep a night, most get only seven. Although most people tend to minimize the effects of insufficient sleep as simply feeling a bit tired, studies of sleep-deprived people have shown that they are less efficient and more irritable. Those who accumulate a large sleep debt experience "attentional lapses, reduced short-term memory capacity, impaired judgment and the occurrence of micro sleeps.”
To sleep better:
Avoid caffeine, nicotine and alcohol in the late afternoon and evening; exercise regularly, but do it at least three hours before bedtime; establish a relaxing bedtime routine like taking a hot bath or meditating; use your bed only for sleeping and sex, not for reading or watching television; get out of bed if you don't fall asleep within half an hour, go to sleep and wake up at the same time every day, even on weekends, and, if you have trouble falling asleep at night, avoid daytime naps.
Recent studies have shown that when all clues to time are removed and people are permitted to sleep as much as they choose, they sleep 10.3 hours out of every 24, just as monkeys and apes do.
Simply resting is not an adequate substitute for sleep. If you get sleepy when you are bored or sitting quietly in a warm or dark room or trying to read or listen to a concert or lecture, you are sleep-deprived.
