go downhill?

[keannu]

Is go downhill a figurative meaning for "don't work out"? Is it a common expression?

ex)John was as famous for his tennis skills as he was for his fits of temper on the court. One afternoon, I was playing an important singles match against John. When things didn't go his way, he began to go downhill, complaining about the game, screaming at himself, and slamming his racket....

[kiwi man]

NOT A TEACHER!

It means something along the line of things start to get worse.

[JTRiff]

Not a teacher

It's very common. Ones heath can go downhill, one's career or lifeor just about anything can go 'downhill' meaning, get worse.