put a damper on
Discourage, dishearten, deter, as in Grandpa's death put a damper on our Christmas holidays. This idiom employs the noun damper in the sense of “something that damps or depresses the spirits,” a usage dating from the mid-1700s.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.