01/20/2015 08:21 am ET Updated Jan 20, 2015

How To Figure Out How Much Sleep You Really Need

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Sleep takes up one-third of our lives, but it puzzles us so much.

Many of us are tired all the time -- 40 percent of Americans sleep less than the recommended seven to nine hours, and according to a recent poll by the National Sleep Foundation, 35 percent of Americans say their sleep quality is "poor" or "only fair."

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