system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we constantly rub our eyes when we're tired?
gpt
If we haven't slept in a while, our eyes begin to hurt or itch. This is because, as humans, we rely heavily on our sense of sight. Because of this, our eyes get no rest while we are awake. Whether it's blinking, straining or simply focusing our sight, our eye muscles are constantly at work. When we sleep, we can finally close are eyes and let them rest without having to see anything. With all of this in mind, rubbing our eyes is a way of sort of massaging the muscles around our eyes as we would if we had a sore wrist. The more tired we are and the less we've slept, the more our eye muscles get tired and want to relax. Hope this helped :)