system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 : Why am I tired when I wake up from 8+ hours of sleeping ?

Title. I need to know please. Thanks ! :)
gpt
Think of your sleep cycle as a roller coaster. You go up, you go down, you go up, you do gown, and you do that many many times during the night. Deep sleep, light sleep, deep sleep, light sleep, etc...

 Think of waking up like getting off the roller coaster. If you get off the roller coaster on the bottom near the ground, it's easy, safe, and you feel rejuvenated and fresh. If you try to get off at the top, you'll end up falling a long distance, hit the ground, and you will feel awful. 

It's important to try and time your alarm clock to wake you up at the proper point on the roller coaster. Each "up and down" takes about 90 minutes, so try to schedule your wake up time so it's in an interval of 90 minutes from when you fell asleep. That should place you near the ground when you wake up.