Learn English – An idiom for taking advantage of something which gave you the right to take advantage in the first place

Interestingly, English has almost the same expression: "fishing in troubled waters", going back to at least the 16th century.

It seems to originate in a belief among fishermen that fish rise to the surface in foul weather and may be more readily netted—hence the phrase "mackerel gale", a storm which promises a good catch.

But very early it was applied figuratively to just such situations as yours. Grafton's Chronicle and Foxe's Actes & Monuments (both 1569) quote a letter from Pope Innocent III warning King John of England not to trust those who advise him to dispute the authority of the Church:

Settle not yourself to obey their persuasions, which always desire your unquietness, whereby they may fish the better in the water when it is troubled.

I have not yet found their source for this; if authentic, it takes the phrase back to 1208 and, presumably, in Latin.

Here are three, often ironical or derisory(source brainy-quote),

'Good job, awesome, well done,'

but this song from 'Life of Brian' would show that I really meant it.

Always look on the bright side of life.