system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do animals and mammals shut down to sleep. Why can’t we keep active while the body repairs itself?
gpt
At the end of the day, we don't know.  There are things that happen with memory processing during sleep (which is why dreams can be so hard to remember).  It's also a good idea for our bodies to shut down during dreams (which again, we don't fully understand why we do that).  Acting out dreams is a quick way to get injured so we don't want to do that.