Endless Energy (get the book or audiobook) by Peter Hollins is a guide to becoming insanely energetic.

How do we improve our sleep?

The first step is to understand your sleep biology, and the next is to learn to work with it so you’re waking up refreshed each morning and with a full “tank.” Your circadian rhythm is your body’s own inbuilt sense of when to wake and when to sleep. Parts of your body perceive and respond to changes in light around you and move through cycles, with physical and behavioral changes occurring over a twenty-four-hour period.

Interfere with this cycle and you push against your body’s own physiological “clock.” A common way we all do this is to surround ourselves with harsh, artificial light at times of the day that our ancestors would have spent in darkness or low light. Your rhythms are set by light in the environment. If you’re in the habit of using LED displays on devices a few hours before bed, starting to phase them out can do wonders for your sleep quality. If you must use these devices, install apps that turn down the blue light and amp up the yellow, or else dial down the screen brightness completely.

Just as fading light signals bedtime to your body, bright light indicates that it’s time to wake up. When you wake up in the morning, make a habit of exposing yourself to bright sunlight as soon as possible after you wake, to kick-start your system. In fact, when it comes to sleep, routine and consistency are the goal. Pay attention to the times you wake up and go to sleep, and maintain a fixed routine, making sure to keep your sleeping hours properly dark and your waking hours as bright as possible. Do everything you can to cut down on blinking lights in your bedroom, and invest in blackout curtains, especially in summer. Keep naps to a minimum (twenty minutes at most) and time them for early afternoon, no later.

Finally, take some time to figure out your “chronotype”—i.e., your unique pattern of wakefulness. Are you an early riser who goes to bed early too? Or are you a night owl who only really peps up at around 10:30 in the morning? We’re all different, and this has been borne out through psychological testing and categorizing of people into larks (early birds) or night owls. The key is to recognize and respect your own needs and limitations. If you’ve always been someone who falls asleep early in the evening, go with it. Wake early, do most of your work and exercise in the morning, and allow yourself to cycle down naturally as the day wears on. Make adjustments so that you work with rather than against your natural rhythms.

Mental and emotional factors play heavily into the quality of sleep, too. We know that a poor night’s sleep will leave you feeling bad during the day, but the experiences you have in your waking life can carry over to your sleep, too. In fact, many people’s sleep disorders are vicious cycles, and reinforcing behaviors that keep poor sleep habits going.

Do whatever you can to reduce stress in your life. Take frequent breaks throughout the day. Even a five-minute pause to meditate quietly or focus on deep breathing is enough to lower your cortisol levels and help you find your center again. One of the best things you can do to improve your sleep quality is to have a daily bedtime ritual you can depend on. You can decide on exactly what will work for you, but the important thing is that it’s a habit, and it’s something that signals your body that it’s time for sleep.

Do stressful, energetic things earlier on in the day and save quieter, slower activities for before bed. Avoid excess stimulation (like exercise, stressful work, emotional arguments or upsetting TV) in the evening and do things that calm you down. A hot bath, visualization, massage, yoga, a little light reading, or taking the time to do a little beauty ritual will all put you in a relaxed state of mind.

If you’re someone who has difficulty with insomnia or poor sleep hygiene, a big part of your ritual will be to program yourself with a more relaxed attitude toward sleep in general. Deliberately take the time to wind down and empty your thoughts. Tell yourself it’s not the end of the world if you don’t sleep properly; just relax, take your time, and rest. If you haven’t fallen asleep after around twenty minutes, get up out of bed and go somewhere else to do a calming activity. A cup of tea, a doodle in a journal or listening to a quiet podcast are all great ideas.

Insomnia can feed on itself if you allow yourself to worry that you’re not sleeping well. Your attitude toward sleep is just as important as the more practical factors. Actively remind yourself, “It’s OK if I don’t fall asleep. I’ll still get rest even if I just hang out here for a while.” Don’t put pressure on yourself to “sleep right.” What could be more un-relaxing than that?

If you can’t fall asleep, don’t linger in bed, or else you may create negative associations with that space. It’s a good idea to reserve this area for sleep and sex solely. You might find that spending a little time making your own “sleep sanctuary” goes a long way toward telling your unconscious mind what to expect when you get into bed. Choose relaxing, decluttered décor. Good-quality bedding, blackout curtains, breathable pajamas, and possibly sleep masks and earplugs will do wonders. Ensure your mattress is firm and doesn’t keep you overly hot, and that the room is quiet, dark, and slightly colder than you’d normally like. Make sure there’s good air flow without any drafts. Do something about snoring partners and/or pets who hog all the space! Get yourself a pillow you love and you’re ready to go.

Finally, if you’re a frequent flyer or find yourself sleeping in hotels often, take some time to figure out ways to mediate the disruption. Over-the-counter melatonin pills can help with jet lag, and the occasional sleeping pill or natural remedy can help break a bad sleep cycle—when used only very occasionally, that is.

Overall, there’s a lot you can do to honor your natural limits and needs, and work with your biology rather than fight it (in case you haven’t noticed, the latter never works out well anyway.) And this goes beyond just ensuring you get better sleep. Your circadian rhythm is about the complete ebb and flow of your energy throughout the day. There are certain times you’re going to be more active and energized, and others you’re going to be more mellow. Knowing when these times occur means you can schedule your life to better fit your natural cycles.

People are not machines with uniform, unwavering energy levels no matter the time of day. Firstly, bear in mind that there is nothing innately superior about being a “morning person,” and you won’t magically be more productive just because you forced yourself to wake up early or get more things done before lunchtime. As we’ve seen, this advice works for some chronotypes, but not everyone will actually be more productive this way.

The old “early to bed, early to rise” wisdom is not for everyone, in other words. Rather, you need to look at the times when your body is naturally more awake, and make sure you’ve scheduled your work to coincide with that. It doesn’t matter whether this is comfortably done in the morning or almost midnight—if it fits your chronotype and energy levels, it works.

How do you find your “peak hours”? First, become curious about your actual habits over a period of a week. Note the times of day you were most productive. Look for patterns not just in energy levels, but enthusiasm and emotions, too. Look for what inspires energy outbursts, and when you have the most output, work-wise.

Now, the obvious next step is to make sure you’re taking advantage of that energy spike by “booking” these peak hours and managing your other less important or less demanding tasks outside that window. Essentially, you are budgeting and managing your energy just as you would your time and money, using what you have most efficiently.

Another way to look at it is by taking the circadian rhythm and extrapolating it into our ultradian rhythms, which are the rhythms that move with us through the twenty-four-hour cycle of our lives. Sleep researcher Neil Kleitman identified the presence and importance of rapid eye movement (REM) sleep and discovered that the body generally operates in ninety-minute cycles, moving progressively through periods of higher and lower alertness.

In other words, our energy and alertness come in ninety-minute chunks. These ninety-minute cycles apply whether we are awake or asleep, and we can use this information in a few ways.

First, we now know there is essentially a time limit to energetic and productive thinking. It’s not endless; in fact, it might be capped at ninety minutes at a time. At the end of an intense ninety-minute work period, we grow fatigued and begin relying on stress hormones for energy. Then, suffering from overload, the prefrontal cortex begins to shut down, and we move into fight-or-flight mode. We may attempt to override the body’s signals by fueling ourselves with caffeine and sugar, but in the end, our focus and concentration suffer.

Additional research from the U.S. Army Research Institute backs up the findings and supports the ninety-minute periods of focus and energy. The point here is to listen to your body. It is telling you exactly how it prefers to function.

Besides creating ninety-minute cycles, the ultradian rhythm also distributes these peaks and dips of energy throughout a twenty-four-hour period in specific ways. There are certain times when you can maximize your thinking, and others when you are setting yourself up for failure. Of course, keep in mind, these are averages, and outliers do exist.

As we move through a typical day, it takes a few hours after waking to reach our peak levels of energy and alertness. For many people, the late morning hours, after 10:00 a.m., represent the highest period of mental sharpness and focus. This is when you might take advantage of your brain functioning at its peak. But remember, you probably have only ninety minutes on average.

Soon after lunch, our energy levels begin to decline.

According to Christopher Barnes’s writing in the Harvard Business Review, our body’s energy naturally dips somewhere between 2:00 and 3:00 p.m., possibly because we are at the midpoint of our wake cycle. For thousands of years, humans have rested during the afternoon (think of the Spanish concept of the midday siesta or nap), and only since the Industrial Revolution imposed an emphasis on mass productivity have we begun to eliminate this critical period of rest for the nine-to-five workday.

After we hit that afternoon dip, our energy levels begin rising again, and we generally hit our second peak around 6:00 p.m. As the evening wears on, our energy diminishes, slowly transitioning into sleep cycles.

The ultradian rhythm of energy is something that rules our day-to-day existence. You can fight it, but why would you? Work within the simple guideline it lays out for your energy, and you will find that smarter thinking becomes the rule rather than the exception.

So, we’ve seen how to tackle and work with sleep, circadian, and ultradian rhythms. Another obvious—but no less critical—aspect to master is your physical well-being. It’s easy to imagine we are all just giant heads walking around on stalks, but the fact is that nothing happens in life without the body being in good condition. We all know about the importance of eating a diet that’s balanced and optimal for health, but how many of us specifically eat to manage and maintain our energy levels?