system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we sometimes feel more awake if we slept very little (less than 5 hours) than if we slept a normal amount (7 - 8 hours)?

Today I woke up at 5 am, hours before my alarm. Yet I felt more rested than I did yesterday when I woke up on time and slept for about 8 hours. Why are our brains so weird?
gpt
If you wake up betweem REM sleeps, you feel fine. Interupting a REM sleep makes you feel exhausted. If im not mistaken we get like up to 6 REM sleeps per night. After reaching 3 you could feel fine. But waking up halfway in REM sleep could make you feel exhausted.