system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come sleeping too much makes you feel tired?

To clarify: I'm not asking for a cure to this problem, but a scientific explanation as to why.   Thank you.
gpt
It all depends. Your body goes through 90 minute sleep cycles, and if you so happened to wake up in between these sleep cycles, you'll be alert and refreshed. If you wake up during a sleep cycle, you'll be groggy and sluggish. For example, if you go to sleep at 10:30 PM, your sleep cycles will end at midnight, 1:30, 3:00, 4:30, 6:00, 7:30, 9:00, 10:30, etc. So if you wake up at 7:30, you'll be more rested than if you woke up at 8:15, despite getting more sleep if you woke up at 8:15.
       
I hope this clears things up for you :)