Once upon a time a fleet of flying saucers approached planet Earth. Just outside the orbit of the Moon, they encountered an Angel, who said unto them, "Greetings, space travelers! I welcome you in peace if you come in peace; for peace is plan A, whose failure is not an option."
But the aliens said, "We do not come in peace, we come to conquer, for conquest is our own plan A, whose failure is also not an option."
The Angel said, "Dear fellow-beings, I pray that you reconsider! Failure is never an option, but it is always a possibility! Strife yields grief; only harmony brings fulfillment; for that is the Law. Therefore let us reason together! Show me a sign of your goodwill, and all will be well between us."
In reply, the saucer fleet vaporized the Lunar Farside telescope with a gigawatt infra-red laser.
"Alas, alas!" the Angel wailed. "Plan A has failed!"
So the Angel armed its antimatter cannon and fired a volley of pellets at the invading fleet. Each antimatter pellet hit a saucer dead on, and each saucer then exploded with the force of twenty-three thousand tons of TNT.
The fireballs blossomed and cooled, and the Angel wept. “Oh well,” it sighed, “It's good to have a plan B.”
Moral: Talk softly and carry a big stick.