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.

The gross demonstration of caffeine is that it prevents you from falling asleep. The slightly more nefarious aspect of caffeine is that maybe you can fall asleep, but we know that the depth of deep sleep you're getting if caffeine is still in your system is severely less.

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.

Matthew Walker Quotes