While relaxing in bed with your eyes shut is nice, it’s not the equivalent of sleep and isn’t considered part of your needed 7 to 9 hours of shut-eye because your brain is still active. When you’re actually asleep, parts of your brain slow down, your body temperature slows down, and your muscles relax. Good-quality sleep gives your body and brain time to recharge and clear out waste. Poor sleep is linked to various health conditions and diseases, including diabetes, obesity, heart disease, and early death.