As the kids head back to school, I’m thinking about what really leads to success—as well as happiness. Part two in a three-part series. Click here to read Part One.

When we look at people who are at the top of their field, they all have grit: persistence and passion for their long-term goals. But this doesn’t mean that they burn the midnight oil day in and day out in pursuit of achievement.

Just as elite performers are strategic about what they practice, they are also strategic about how long they practice. If you think success requires practicing until your fingers bleed or mind spins or muscles give out, for hour upon hour upon hour of endless, relentless, intrinsically boring practice, I have some good news for you: Research suggests that’s not the way to get there.

In our modern, fast-paced, and technology-driven culture, we sometimes forget that we are humans, not computers. Like other animals, we humans are governed by our ultradian and circadian rhythms. Most people are familiar with the concept of our circadian rhythms: In the twenty-four hour period between when the sun rises and sets, we sleep and wake in predictable cycles. When we travel into different time zones, our circadian rhythms get out of whack, and, as a consequence, our lives also can feel similarly discombobulated.

Our brains and bodies also cycle in “ultradian rhythms” throughout the day and night. An ultradian rhythm is a recurrent period or cycle that repeats throughout the twenty-four hour circadian day, like our breathing or our heart rate.

Our brain-wave patterns cycle in ultradian rhythms as well, and about every hour and a half to two hours, we experience a significant “ultradian dip,” when our energy drops and sleep becomes possible.

When we work through these dips—relying on caffeine, adrenaline, and stress hormones to keep us alert—instead of letting our bodies and brains rest, we become stressed and jittery, and our performance falters.

In his studies of truly great performers, K. Anders Ericsson, the psychologist and author of several landmark studies on elite performance about whom I wrote last week, found that they practiced and rested a lot more than their good but not elite peers. For example, violinists destined to become professional soloists practiced an average of three and a half hours per day, typically in three separate sessions of sixty to ninety minutes each. Good but not great performers, in contrast, typically practiced an average of 1.4 hours per day, with no deliberate rest breaking up their practice session.

So it isn’t just that elite performers work more than others; they rest more, as well. The top violinists mentioned above slept an hour more a night than their less-accomplished classmates. They were also far more likely to take a nap between practice sessions—nearly three hours of napping a week.

Super high achievers sleep significantly more than the average American.

On average, Americans get only six and a half hours of sleep per night. (Even though studies show that 95% of the population needs between seven and eight hours of sleep a night.) Elite performers tend to get 8.6 hours of sleep a night; elite athletes need even more sleep. One study showed that when Stanford swimmers increased their sleep time to ten hours a night, they felt happier, more energetic, and their performance in the pool improved dramatically.

High performance requires more sleep because it involves higher rates of learning and, sometimes, physical growth. When we are awake, adequate sleep allows us to focus our attention on our practice; when we are sleep deprived, our overworked neurons become uncoordinated, and we start having trouble accessing previously learned information.

When we sleep, our brain consolidates what we’ve learned while we were awake, making it a part of our working memory that we can access later. Sleep allows us to remember tomorrow how to do what we’ve practiced today, and it enables us to recall the information and knowledge we’ve just learned.

The amount of sleep that we get—and how disciplined we are about following our body’s natural circadian and ultradian rhythms—affects not just our health but also our productivity and performance. But what does sleep have to do with grit?

Grit is the ability to maintain perseverance and passion toward our long-term goals; we cannot persevere in the face of difficulty if we are fatigued physically, mentally, or emotionally. We can’t persist over the decade or so it takes to achieve true mastery if we become sick or exhausted or burned out along the way. And we can’t improve our skills—intellectually, physically, or artistically—if our learning, memory, and reaction times are impaired due to lack of sleep and rest.

So being gritty isn’t just about pushing yourself 24/7 toward your goals, in both good and bad weather. It’s about making progress toward your goals, consistently and deliberately, in a way that works with our human biology—allowing for proper refueling and consolidation of knowledge.

Read Part 1 of this series here.

Best known for her weekly Happiness Tips, Christine Carter, Ph.D., draws on psychology, sociology, and neuroscience, and uses her own real-world adventures to demonstrate happiness dos and don’ts in action. Dr. Carter is a sociologist at UC Berkeley’s Greater Good Science Center, and the author of RAISING HAPPINESS: 10 Simple Steps for More Joyful Kids and Happier Parents. She teaches happiness classes online throughout the year to a global audience on her website www.christinecarter.com.

*Photo credit NavyJackBell via Flickr.