have a cow

(verb) to lose control of your emotions

Example Sentences:

The poor schoolteacher had a cow and started crying when she won five million dollars in the lottery.

The workers complained to their boss because the manager was always having a cow over unimportant things.

Boyfriend: We need to talk.
Girlfriend: Okay.
Boyfriend: Please don’t have a cow, but I think we should date other people.
Girlfriend: What?! I thought we were going to get married! I hate you!
Boyfriend: I asked you not to have a cow!

From the Blogs:

Parent groups have a cow over campaign pushing chocolate milk as a ‘health food’

Media:

Similar idioms:

1. flip out
2. get carried away
3. blow one’s cool
4. don’t cry over spilled milk
5. food for thought
6. pet peeve