But the problem is a lot of us ARE exhausted in our waking lives. A YouGov poll found that one in eight Brits say they're tired all the time -- a quarter say they're tired most of the time, while a whopping third say they're weary half of the day.
If you're not sure how to tell whether you're sleep-deprived or just run-down, though, Dr Nathaniel Kleitman from the University of Chicago -- also known as "the father of sleep research" -- say all you'll need is a spoon and a metal tray.
The method was devised as part of Dr Kleitman's Sleep Onset Latency Test.
We've written before at HuffPost UK about how taking too long to get to sleep can actually be a sign of "sleep latency," which affects the efficiency of your kip.
But it turns out that falling asleep less than five minutes after your head hits the pillow is a problem too. It can be a sign of sleep deprivation.
On the BBC, Dr Micheal Mosley said that you'll need a watch, a spoon, and a metal tray to find out whether you're affected by the latter condition.
He explains that you should look at your watch before you fall asleep and dangle the spoon over the tray as you do so.
When you do nod off, "the spoon should hit the tray -- bang -- and wake you up."
You can then look at the time to see how long your commute to the land of nod lasted.
Longer than 15 minutes should mean you're okay, Dr Kleitman suggested.
But less than 10 minutes may mean you're sleep-deprived; under five minutes, and the problem could be severe.
Of course, a simpler test would be setting an alarm for 15 minutes and seeing if you fall asleep within that time.
Johns Hopkins Medicine says that other signs of sleep deprivation include drowsiness in the daytime, not being able to concentrate, mood swings, irritability, poor memory, and decreased muscle strength.
In the long term, you may also struggle to fight infection, notice severe mood swings, and face an increased risk for both mental health issues (like depression) and physical health problems (like stroke), they add.
The NHS says that you should see a GP if your sleep pattern affects your day-to-day life, especially if you're not seeing improvements despite making lifestyle changes.