Rain on Someone's Parade

Idiom: Rain on Someone's Parade

Example 1:

John: I'm so excited to see the new Iron Man movie tonight! Let's go to In-n-Out before showtime and get burgers to have dinner in the theater. That sounds like a great idea, right?

Bill: I hate to rain on your parade, but they won't allow outside food in the theater. We can go their early and eat first. 

Example 2: 

Mom: Aren't you excited?! Our camping trip is only 2 days away! Just imagine all the fresh air, hiking, and the sounds of nature! I can't wait!

Teenager: No. I am not excited. There's no WIFI in the woods. I won't be able to text, watch videos, or send Snaps. That doesn't sounds fun at all.

Mom: Well I won't let you rain on my parade! It's going to be great! You'll have fun. I promise!

Meaning: to "rain on someone's parade" is to ruin their good mood or fun plans.

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