Idioms and Phrases with go downhill
Deteriorate, worsen, as in Ever since the recession began, the business has been going downhill. The figurative use of downhill for “decline” dates from the mid-1800s. Also see downhill all the way.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.