Robert A. Heinlein

“Everything is theoretically impossible, until it is done.”

“A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.”

“Never underestimate the power of human stupidity.”

“If you don't like yourself, you can't like other people.”