system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it often hard to sleep even when exhausted/sleep deprived?

Have you ever found yourself feeling somehow "too tired to sleep"? Isn't it super weird when you consciously want something that you know your brain (and rest of your body) needs, and yet it refuses to cooperate? What gives?
gpt
According to the sleep training doctor, Dr. Mark Weissbluth; “sleep begets sleep”. When you sleep it settles your nervous system so it’s easier to sleep in the future. When you miss sleep and have a sleep debt then the nervous system goes crazy and goes on heightened alert essentially making it harder to sleep in the future. It’s kind of a wired but tired kind of thing. The nervous system is wired but you are tired.

The best way to fix this is to stick to a constant sleep schedule. Get up at the same time everyday. Your body will get into a rhythm and you’ll sleep well and much deeper and feel rested. It takes a while to override the nervous system because of sleep debt. Get up at the same time even if you are tired. Eventually your brain will know what is expected and it will relax at the same time every night and it will determine what time you need to go to bed. We all require a different amount of sleep. Your body will tell you when to go to bed if you are telling it what time you want it to get up every single day.