Wiktionary
vb. (context idiomatic English) To worsen or degenerate.
Usage examples of "go downhill".
I turned and went uphill, on the theory that someone following a trail will tend to go downhill, since that is the easiest and swiftest way.
It's weird, you know, because you're thinking all you've got to do is go downhill to the water and come back the same way, and that shouldn't be too tough as long as you pay attention.
The ferocious wind had tempered to occasional playful gusts, and of course it is always easier to go downhill than up.
I have to tell himtellwho ever's carrying himto go downhill, not up!
All you have to do is go downhill until you reach the swamp, turn right until you reach the slide, then go uphill until you reach the Dragons.
I had to fight to hold him in, because the way was icy, and I was afraid of a fall, but I confess that-with Galapas' last remark echoing uncomfortably in my head-I let him go downhill through the trees a good deal too fast for safety, until we reached the mill and the level of the towpath.
The man from Ao-chung clicked the breech-bolt of his gun impatiently, and made as to go downhill.