From
The Art of War by Sun Tzu (Trans. Lionel Giles, 1910):
Hence the saying: If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.
From
The Light Fantastic by Terry Pratchett:
The barbarian chieftain said: "What then are the greatest things that a man may find in life?" This is the sort of thing you're supposed to say to maintain steppe-cred in barbarian circles.
The man on his right thoughtfully drank his cocktail of mare's milk and snowcat blood, and spoke thus: "The crisp horizon of the steppe, the wind in your hair, a fresh horse under you."
The man on his left said: "The cry of the white eagle in the heights, the fall of snow in the forest, a true arrow in your bow."
The chieftain nodded, and said: "Surely it is the sight of your enemy slain, the humiliation of his tribe and the lamentation of his women."
There was a general murmur of whiskery approval at this outrageous display.
Then the chieftain turned respectfully to his guest, a small figure carefully warming his chilblains by the fire, and said: "But our guest, whose name is legend, must tell us truly: What is it that a man may call the greatest things in life?"
The guest paused in the middle of another unsuccessful attempt to light up.
"What shay?" he said, toothlessly.
"I said: What is it that a man may call the greatest things in life?"
The warriors leaned closer. This should be worth hearing.
The guest thought long and hard and then said with deliberation: "Hot water, good dentishtry and shoft lavatory paper."