Trying to Jump to The Moon

idiom
Trying to do something that seems to be impossible

Friend 1 is trying to make an invention without any knowledge about anything related to it.
Friend 2: Hey, stop trying to jump to the moon!

Papa John's Day of Reckoning

noun
1. A time of crisis or need.
2. When you have a bad feeling about a certain moment that is about to happen.

"I'm bad at soccer, so my Papa John's Day of Reckoning is P.E."