I slept eight hours. Why am I still tired?

Almost everyone has had the feeling of sleeping a decent amount, but waking up feeling tired. Don't worry, there are ways to improve your sleep.

Sleep isn't a simple, continuous process. Your body naturally coordinates your bedtime into several segments, which form a continuous sleep cycle. Natural sleep incorporates about four to six of these 90-minute cycles every night, much like workers in a factory changing shifts every few hours.

There are four parts of a sleep cycle: N1, N2, N3, and REM.

• N1 is when you first fall asleep—everything in your body relaxes as you enter a light sleep. You'll easily wake up here, if something manages to disturb you.

• N2 continues the sleep cycle. As you enter this stage, your body slows down even further, and brain activity begins to resemble that of someone in deep slumber. About half the sleep cycle is N2.

• N3 is the deepest sleep. Here, you not only experience the most steady sleep, but your body performs crucial tasks like growth and tissue repair. Some people sleepwalk in this phase.

• Although REM sleep isn't very deep, it's by far the most exciting. During this phase, your brain becomes very active, and your eyes begin to move quickly under your eyelid—hence the name Rapid Eye Movement (REM). Most dreams occur during this stage, so if you ever wonder why dreams feel so real, it's because your brain is actively working! Besides dreaming, REM also helps your brain with memory, learning, and emotions.

So, back to the question: why are you still tired after sleeping "enough"?

The answer is simple: deep sleep only accounts for a small fraction of total sleep. About 20% of every sleep cycle is N3, meaning that you only get about 1.5 hours of very deep sleep in an 8-hour night.

Here are some ways to improve your sleep cycle, maximizing N3 and REM, which are the most important to your brain and body:

• Set a sleep schedule: sleeping at a regular time conditions your body to nightly cycles. Try to maintain the same schedule on weekends. Sometimes, it's helpful to sleep full cycles—plot out 90-minute intervals and adjust your schedule accordingly!

• Keep a tidy environment: a cool, dark, and quiet bedroom is the best for sleep. This ensures you'll pass quickly into deeper sleep. Remember to turn off electronics! Blue light keeps your brain active and makes it harder to sleep.

• Relax before bedtime: read a book, listen to music, or do whatever you find relaxing. This will help condition your body for sleep, and allow you to go into deep sleep faster.

Everyone's sleep is unique, and it's important to note the signs coming from your body so that you're in good health. Don't be afraid to try new sleep techniques, and find out what works best for you. Remember, everyone can work towards a better night's sleep!