There’s nothing quite like the feeling of waking up refreshed after a good night’s sleep. From a mental standpoint, you feel more focused, able to take in new information and handle stress, and from a physical perspective, you’re ready to tackle your day. However, it’s not always easy to get enough rest and the quality of your sleep can have serious consequences for your health and wellbeing.

In fact, research shows that a lack of sleep can damage your brain and body. It can also make you feel moody, weak, and irritable, and it may even lead to weight gain and diabetes. It’s important to prioritize sleep and try to understand what goes on during the different stages of sleep, so you can do your best to improve it.

The science behind how we fall asleep and wake up is complex, but the basics are that you enter into a state of deep, natural sleep when your circadian rhythms tell you to do so. This is controlled by the hypothalamus and thalamus, which are parts of the brain that regulate your internal clock. It’s also controlled by a sleep-wake cycle that occurs in cycles of 90 minutes to two hours. The cyclical nature of sleep and the timing of your circadian rhythms are critical for maintaining optimal health.

A growing body of evidence indicates that sleep is vital for your immune system, allowing it to clear away protein debris and cellular waste. This helps keep the body healthy and reduces inflammation, making it easier to ward off diseases. Sleep is also necessary for the formation of memories, as it helps your brain consolidate them into long-term memories. In addition, it appears to help your body repair itself, which is why you’ll often feel more tired after a strenuous workout or illness.

Another benefit of sleep is that it allows your mind to process emotions. That’s why people who suffer from depression or anxiety often struggle to get enough rest, and it’s also why they’re more likely to have negative emotional reactions. Restful slumber gives your brain time to catch up, which is why it’s important to get plenty of rest.

It’s essential to remember that your sleep is not a luxury. Insufficient or poor-quality sleep can contribute to a wide range of conditions and illnesses, including obesity, cardiovascular disease, high blood pressure, and diabetes. In fact, one study showed that getting sufficient sleep was associated with a reduced risk of developing heart disease, even when controlling for other lifestyle factors such as regular exercise, low cholesterol and blood pressure levels, a healthy diet, and nonsmoking status.