Did you ever wake up from what you thought was a long night of sleep and feel exhausted? Alternatively, did you ever wake up from a short sleeping night and feel refreshed? I've been deep into Matthew Walker's best-seller Why We Sleep: Unlocking the Power of Sleep and Dreams and, if you read it, you'll realize that there are dozens of reasons why this happens.

But if you can't just go on instinct, then how do you know if you got enough sleep? Experts like Walker say it comes down to two simple questions.

10 a.m. cat nap

After waking up in the morning, could you fall back to sleep at 10 or 11 a.m.?

I am an advocate of naps and have been a practitioner for decades (which came in handy when I became a parent). However, waking up at 7 a.m. and being ready to snooze at 10 a.m. isn't a nap. It's a signal that you didn't sleep enough the night before.

Walker says it is an indicator that "your sleep is not high enough quality or quantity."

Quantity may feel like the obvious one: Of course, you'll feel tired if you worked until 3 a.m. last night and woke up at 7 a.m. But it isn't always the semi-all-nighter that's the culprit. Sleep scientists say we should get eight to nine hours of deep sleep per night to be at our sharpest tomorrow. This amount of sleep also helps us solidify what we've learned the previous day, preventing all the hard work we did yesterday from being a waste of time.

Quality is a little more complicated, as several factors can prevent us from having high-quality sleep. Again, I have young kids, so external factors have made my sleep, and my partner's sleep -- as a scientist may say -- suboptimal. Lesser acknowledged elements, though, are bright lights before bed, erratic bedtimes, alcohol or caffeine before bed, and excessive mobile device reading less than three hours before tucking in.

No coffee necessary

Can you function optimally without caffeine before noon?

This is a tough one for most productive people, I know. I share a new coffee study about once a year, and every time I get a combination of fear, dismay, and denial. I understand. Until a few years ago, my coffee fix came in right after breakfast. Now, it alternates between late morning and mid-afternoon.

Need coffee first thing in the morning? Walker puts it like this: "You are most likely self-medicating."

And, as I've learned recently, decaf has 15 to 30 percent of the caffeine that regular coffee contains. In short, a couple cups of decaf can be just as self-medicating as one cup of joe.

How to sleep better

Walker shared some sound advice when I heard him speak at TED 2019. Here are the highlights:

  • Get out of bed when you can't sleep and do a low-impact activity until you feel sleepy;
  • be consistent in when you go to bed and when you wake up; and
  • leave the phone and other mobile devices out of the bedroom.

Still not sure where you stand? It may be worth skipping the morning coffee today and seeing how you really feel.