go south 悪化する

go southは色々な解釈が可能ですが、基本的な意味は悪化するです。 2:35 I guarantee you that at some point, everything's going to go south on you, and you're going to say this is it. ある時点で全てがうまく行かなくなり、ついにこれまでかという時が来る。

The Martian | Teaser Trailer [HD] | 20th Century FOX
https://www.youtube.com/watch?v=5b4Apurqp2s  4:41 that his career was about to take off. but it was all about to go south. 　
Years Before Shooting, Vester Flanagan's Big TV Break Turned Sour
https://www.youtube.com/watch?v=8O6zKglOiZo  1:09 production has been pushed south.
Heavy smog engulfs Shanghai https://www.youtube.com/watch?v=nzbzSbfgQjg  1:10 if they go south, you can't recovery from it. いったん地球環境が悪化すれば、回復は無理だ。
Raw Video: President Obama in Omaha
https://www.youtube.com/watch?v=bOHaddfShI4  7:37 things began to go south 事態は悪化し始めた
Top 10 Worst Attacks on Journalists

参考リンク
http://bridge-english.blogspot.jp/2010/04/north-of.html  north ofとは？
http://bridge-english.blogspot.jp/2013/09/south-of.html  south of とは？

練習問題解答
a-4629 go south
a-5671 went south
a-9875 sent Wall Street south