Gilda

Short term sleep deprivation can cause many of the same personality changes as being legally drunk--impaired judgement, physical reactions, heightened or dulled emotions.

The amount of sleep needed varies greatly from person to person. I can't sleep more than about 5 hours a night, and usually go to bed around 1 am, getting up at 5:30. I'll take a nap at about 5:30 in the afternoon, and by 6:300 I'm up and ready to go for the rest of the evening, but god help my SO and the world if I don't get my nap time.

This has been pretty consisten for the last ten years or so, since I started college. The only time it really changes is the last couple of days before my period, particularly if I'm cramping badly, when I might find myself climbing into bed at 10:00 or up till 3:00.

A consistent sleep pattern that allows you to operate fully alert the entire day is important. You can lose more productivity due to inefficency than to time. Try picking a consistent bed time and a consistent rising time, and stick to it for a week. If you're getting gradually more tired as the week goes on, add a half hour to the sleep duration and try the next week. Repeat until you have as much energy at the end of the week as at the beginning, and you have the amount of sleep you need.

Also, don't be afraid of napping in the afternoon, especially if you have one of those late nights planned. A half hour nap won't appreciably cut into your productive time, and can give you a big boost for the remainder of the evening.