system
Given the following post, respond as if you're commenting on Reddit:
human
Why does sleep feel *so* good?
gpt
Anything that you need to survive feels good when you need it. 

Try not breathing (for just a few seconds) and see how good that first breath feels. Or try not eating for several hours past mealtime. You feel very hungry, and the food tastes *so* good. Sleep is the same way. When you need sleep, it feels very good because that's what your body needs.

This is because of evolution. Creatures that didn't enjoy eating, sleeping, or breathing wouldn't live very long, and wouldn't have much of a chance to make baby creatures like them. Creatures that did survived longer, and had little baby creatures that liked the same things.

This is part of the reason why Mommy and Daddy love each other so much, too. Creatures who *ahem* love each other are more likely to survive and have babies. You'll learn more about that when you're older. You'd just think it's yucky right now. (There's a lot of kissing.)