We know that efficiency and effectiveness are increased when you're getting sufficient sleep, and it will take you longer to do the same thing on an underslept brain, which means you end up having to stay awake longer. So goes the vicious cycle.

Do you tend to sleep in during the weekends? That usually signals that you're trying to sleep off a debt you've accumulated during the week.

If you were not to set an alarm clock, would you sleep past it? If the answer is yes, then there is clearly more sleep that is needed.

Matthew Walker Quotes