Several years ago, I went to Norway to visit the farm that has been in my husband’s family for fourteen generations. I fell in love with pretty much everything, including his relatives who still live and work on farm and only speak Norwegian. If I’m being honest, the waffles with jam were also very nice.

I quickly signed up on Duolingo to learn Norwegian and vowed to return one day and speak with my husband’s family.

For a variety of reasons, including a pandemic, we haven’t made it back for that conversation. But I have practiced Norwegian on Duolingo every single day for the last 1750 days, or nearly five years. Part of that practice includes a word matching game, where you progress through levels until you have just a minute and forty-three seconds to match 145 words with their Norwegian counterpart.

That’s just 0.7 seconds per match.

It’s difficult, but after five years of practice, I’ve gotten very good at this game. It’s also a fascinating window into the variables that impact performance.

At my best, I can complete this game with about 15 seconds to spare. If I’m distracted, either because a cat is crying for my attention or because I’m still thinking about something else, I might finish with only 5 seconds to spare, a 67% decrease. If I’m tired, especially mentally tired, then I might not complete all the matches in time.

We’re talking a difference of seconds, sure, but these are huge relative decrements in performance considering that the task isn’t changing in scope or difficulty.

I started paying attention to what was happening when my times got worse. The first thing I noticed was an increase in mistakes. Again, I know the right answer, I’d just pick the wrong word. In sports, we’d call this an unforced error.

I also noticed that the more tired I became, the more my vision was affected. When we describe someone who’s tired as bleary-eyed, it turns out that’s exactly what they are experiencing. I literally couldn't see the words as sharply as when I was rested.

If I’m downright exhausted, I have all that plus slow cognition. It’s like my brain is trying to swim through mud.

None of this is due to not sleeping enough at night. I get great sleep. If I didn’t, the effects would be much greater, probably enough that I wouldn’t be competitive at the hardest level at all.

Chances are you’re nodding along, saying to yourself, “Yes, yes, so important to be rested!”

But how often are you multi-tasking, getting distracted, scheduling back-to-back (to back) meetings, working your way through a to-do list a mile long, then coming home with your body and brain feeling like jello?

For some of you, the answer is nearly every day.

And it’s costing you. You just can’t see it, because you rarely have a highly repeatable, easily measurable task that shows you the difference.

What the research shows, even outside my stunning Duolingo study, is that when you're fatigued, you’re missing things, making mistakes, or reacting too slowly. As your cognitive power slows further, it takes you longer to accomplish the work you already have. Your to-do list grows ever longer. It’s a vicious cycle.

If you’ve been at this a while, you might feel like nothing short of five weeks in Central America will restore your energy and cognition.

I’m never going to tell you not to go play on the beach and eat papayas the size of your head. But what’s more important is what you do when you get back. You can’t vacation your way out of this problem.

If you really care about your performance (and by extension, your work), then figuring out how to manage your energy throughout the day ought to be a top priority.

I like what Steve Magness, who has worked with elite athletes and professional sports teams, says about how to craft a schedule that optimizes performance: mostly easy, occasionally hard, and very occasionally “go see God.”

That’s a good rule of thumb, and probably very different from how most of your days are scheduled now. If you can’t figure out what that means in advance though, simple pay attention to your body. It’s telling you what it needs, you’re probably just so busy, you’re not hearing it.

In practical terms, you probably need to move some tasks from your to-do list to the back burner, at least in the short term, so that you have space to take more breaks and give more thought/insight to how tasks more effectively. Or you may discover you don't need to do them at all.

You also need to pay attention to how your mental state, not just your workload, is impacting your perception of fatigue.

If there’s one thing I wish people understood on this topic, it’s this: A failure to rest doesn’t just slow you down, it stunts your growth.

This may sound funny coming from a coach, but all that self-help stuff you’re doing is like learning how to decorate a cake that you didn’t add baking powder to. It’s like trying to drive across country with a flat tire but new rims.

Sounds silly, right? So stop it. Don’t try to do more, try to do better.

Rest isn’t the absence of work, but a foundational part of the work. So give yourself permission to rest as if your performance (and health, well-being, and long-term success) depend on it. Because they do.