system
Given the following post, respond as if you're commenting on Reddit:
human
(Eli5) Why do we have to “fall asleep” to regain energy?

I’ve always wondered.. why do we have to actually “fall asleep” in order to be rested for another day? Why can’t a person just close their eyes and lie completely still for their body to recover? What does “sleeping” actually regenerate?
gpt
Think of your body as a restaurant. While you're awake, it's open and the kitchen and dining room is full of people. There's no way to clean, bring in new supplies, or fix issues with the building.

You have to have a period of time when the rooms are not in use to do a full clean and resupply. This is sleep. It forces us to shut down our brain and bodies for cleaning and repair.