The important thing is not to shout at this point, Vimes told himself. Do not ... what do they call it ... go spare? Treat this as a learning exercise. Find out why the world is not as you thought it was. Assemble the facts, digest the information, consider the implications. Then go spare. But with precision.

• Terry Pratchett, Thud!

[I have had cause to apply this one recently. It particularly resonated to see it in the book just now.]