Our culture constantly tells you to do whatever you can to stay at maximum potential, even if that includes five cups of coffee in a single day. But when bedtime comes, true rest is elusive. Many entrepreneurs spend nights churning over the day's problems and the next day's worries.

Related: Why Are We Always So Tired?

These seven science-backed tips can help exhausted entrepreneurs recharge at night.

1. Retrain your brain.

Switch off stress by retraining your brain. Instead of pondering worries at night, replay everything you're thankful for. Think only of positive things. According to Harvard research, "Gratitude is strongly and consistently associated with greater happiness. Gratitude helps people feel more positive emotions, relish good experiences, improve their health, deal with adversity and build strong relationships."

Related: 4 Ways to Cultivate a Better Attitude About Your Life

2. Use the bedroom only for sleep and sex.

Reserve your bedroom for sleep and sex. Put your laptop away, and resist the urge to watch TV in bed. You can train your body to fall asleep more quickly if you remove common bedroom stimulants.

3. Don't exercise or eat within two hours of bedtime.

Both of these activities cause chemical reactions in your body that can prevent you from falling asleep.

Related: Rest Well, Live Well: 10 Sleep Hacks to Help You Live Your Best Life

4. Manipulate caffeine's effects on your metabolism.

Did you know caffeine will stay in your body long after you've had your last cup of joe for the day? For some people, caffeine remains in the system for up to 15 hours. Pay attention to how many milligrams of caffeine are present in the foods and beverages you consume every day. This nifty tool can help.

Every individual is different. Your enzymes might break down caffeine more quickly or more slowly, depending on many factors. A good rule of thumb: An afternoon coffee still can affect your sleep at night. Unfortunately, cutting back on coffee isn't always the best option for entrepreneurs.

5. Steer clear of daytime naps.

Train your body to sleep only at night. Taking daytime naps will alter your sleep-wake cycle, and you'll have a harder time falling asleep at night.

6. Don't stare at the clock.

If you must, hide it under a blanket to avoid the temptation.

7. Try a relaxing activity.

If you still can't fall asleep, get up and move to a quiet room where you can read or perform another calming activity until you feel tired again.