put a damper on

US /pʊt ə ˈdæmpər ɑn/
UK /pʊt ə ˈdæmpər ɑn/
"put a damper on" picture
1.

水を差す, 台無しにする

to have a negative effect on something, making it less enjoyable or successful

:
The bad weather really put a damper on our picnic plans.
悪天候が私たちのピクニック計画に本当に水を差した
His negative attitude always puts a damper on team morale.
彼の否定的な態度はいつもチームの士気に水を差す