HomeIt is hard to be lucky all the time
I recently read Be anonymous by software engineer 'Kash'. It mentions the story of the tech savvy proprietor of the illegal darkweb marketplace 'AlphaBay' who got caught due to a digital slip up he made years in the past.
To catch a criminal, law enforcement only have to get lucky once. On the other hand, to get caught criminals only have to get unlucky once. It's a tough row to hoe.
See also: this use of the "need to be lucky always" requirement in a different context:
Mrs. Thatcher will now realise that Britain cannot occupy our country and torture our prisoners and shoot our people in their own streets and get away with it. Today we were unlucky, but remember we only have to be lucky once. You will have to be lucky always. Give Ireland peace and there will be no more war. Wikipedia
https://commons.wikimedia.org/wiki/File:4-leaf_clover.JPG