"Damn it," he mumbled apologetically, "things like this never happened to Vorthalia the Bold." She raised a thoughtful eyebrow. "How do you know? The… - Lois McMaster Bujold

“Never underestimate the human capacity for wishful thinking and willful blindness,” said Miles. Such as a whole society of people who became so wrapped up in avoiding death, they forgot to be alive?

A few other works, half of which turn out to be rubbish. Always a problem with written sources, which frequently tell you far more about the person who wrote them than the subject addressed.

Once you had delegated the best people to do a job for you, you had to trust both them and your judgment.