We’re all good when it suits us, he used to say: that doesn’t count. It’s when you want so badly to do something wrong—when you’re about to make a fortune from a dishonest deal, or kiss the lovely lips of your neighbor’s wife, or tell a lie to get yourself out of terrible trouble—that’s when you need the rules. Your integrity is like a sword, he would say: you shouldn’t wave it until you’re about to put it to the test.
Ken Follett (2011). “Ken Follett EPIC HISTORICAL COLLECTION”, p.2432, Penguin