You probably know that getting enough sleep is important for good health. An occasional night of bad sleep is usually not a big concern. Frequent poor sleep or insomnia is more worrisome. Chronic lack of adequate sleep can cause problems like memory issues, lower immune function, and decreased pain tolerance.
So, how much sleep is enough? Most adults need 7 to 8 hours of sleep. I have read that some people need as little as 5 hours or as much as 10 hours. You can increase your odds of getting a good night’s rest by practicing habits that help your body get ready for sleep. The University of Maryland Medical Center has a good summary of these recommended habits on the UMM sleep hygiene page.
It may be the case, however, that you don’t need your 7-8 hours (or whatever the right amount is for you) to be uninterrupted. This BBC article is about research on how people slept before candles and other artificial lights were widely available. It seems that a common thing was to sleep 3 or 4 hours and then be awake for quite a while before going back to sleep. See The Myth of the Eight-Hour Sleepfor more. I thought it was a very interesting piece.