jump the gun

(verb) to act before the proper or correct time

Example Sentences:

A: Look at that girl over there. She’s so beautiful. I think I’m going to ask her to marry me!
B: There’s no need to jump the gun. Maybe you should ask her to dance first….

The nervous young student jumped the gun when he went to his exam 5 hours early.

Teenager: I’m going to go to Harvard and do an Undergraduate degree. Then I’m going to study Law, and become a successful and rich lawyer. After that, I’m going to go into politics and maybe become the President.
Dad: Okay son, but aren’t you jumping the gun. Focus on getting into Harvard first, and then make your decisions.

Media:

Similar idioms:

1. don’t count your chickens before they’ve hatched
2. live up to
3. plan B
4. back-up plan
5. cut it