“Assumptions are dangerous things to make, and like all dangerous things to make--bombs for instance, or strawberry shortcake--if you make even the tiniest mistake you can find yourself in terrible trouble. Making assumptions simply means believing things are a certain way with little or no evidence that shows you are correct, and you can see how this can lead to terrible trouble. For instance, one morning you might wake up and make the assumption that your bed was in the same place that it always was, even though you would have no real evidence that this was so. But when you got out of your bed, you might discover that it has floated out to sea, and now you would be in terrible trouble all because of the incorrect assumption that you'd made. You can see that it is better not to make too many assumptions, particularly in the morning.”

Source: Mandie and the Courtroom Battle

Source: Why Men Marry Bitches: A Woman's Guide to Winning Her Man's Heart

Source: Memory, Sorrow, and Thorn, The Dragonbone Chair (1988), Chapter 42, “Beneath the Uduntree” (p. 718).
Context: “Never make your home in a place,” the old man had said, too lazy in the spring warmth to do more than wag a finger. “Make a home for yourself inside your own head. You’ll find what you need to furnish it—memory, friends you can trust, love of learning, and other such things.” Morgenes had grinned. “That way it will go with you wherever you journey. You’ll never lack for a home—unless you lose your head, of course...”

The Four Agreements (1997)

Source: Pink Smog

Source: The Four Pillars of Investing (2002), Chapter 2, Measuring The Beast, p. 53.

Book I, Chapter 2, "Some Objections"
Mere Christianity (1952)
Context: The most dangerous thing you can do is to take any one impulse of your own nature and set it up as the thing you ought to follow at all costs. There is not one of them which will not make us into devils if we set it up as an absolute guide. You might think love of humanity in general was safe, but it is not. If you leave out justice you will find yourself breaking agreements and faking evidence in trials "for the sake of humanity", and become in the end a cruel and treacherous man.

From Richard Branson's blog ‘Learning from mistakes’ on the Virgin Website