Rain on somebody’s parade
Definition 1 of 1
Pro Tip 1/3Negative Impact
Implies that the action has an unintended negative effect on someone's mood or situation. 
When I mentioned the poor weather, I didn't mean to rain on your parade.
Pro Tip 2/3Not Literal
It's a metaphorical expression and does not involve actual rain or a parade. 
That penalty call really rained on our parade during the game.
Pro Tip 3/3Apologetic Tone
Often used with an apologetic tone when the speaker is aware that they might upset someone. 
Sorry to rain on your parade, but your car has a flat tire.