system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why is is still hard to fall asleep when you’re sleep deprived?
gpt
When you're sleepy but want it need to stay awake, your body will produce a bunch of chemicals that will help you do so - adrenalin and others, depending on a number of factors.

When you finally want to go to sleep, but your body is still flooded with those, is going to be pretty hard until they're reabsorbed. If you have a lot on your mind still, it could be that your brain keeps making more.