“Anxiety is a useful tool: it forces us to make plans. But when too much anxiety freezes us into indecision, it needs checking.”

Source: The Black Swan: The Impact of the Highly Improbable (2007), p. 162

All Gall Is Divided (1952)

"Zeitgeist and Poltergeist; or, Are Movies Going to Pieces?" http://www.paulrossen.com/paulinekael/aremoviespieces.html (December 1964), from I Lost It at the Movies (1965).

Source: Heidi

Source: The Witch of Portobello (2007), p. 152.
Context: You are what you believe yourself to be.
Don't be like those people who believe in "positive thinking" and tell themselves that they're loved and strong and capable. You don't need to do that because you know it already. And when you doubt it — which happens, I think, quite often at this stage of evolution — do as I suggested. Instead of trying to prove that you're better than you think, just laugh. Laugh at your worries and insecurities. View your anxieties with humor. It will be difficult at first, but you'll gradually get used to it. Now go back and meet all those people who think you know everything. Convince yourself that they're right, because we all know everything, it's merely a question of believing.
Believe.

Speech to students at Cambridge University (4 December 1857)
Context: People talk of the sacrifice I have made in spending so much of my life in Africa. Can that be called a sacrifice which is simply paid back as a small part of a great debt owing to our God, which we can never repay? Is that a sacrifice which brings its own blest reward in healthful activity, the consciousness of doing good, peace of mind, and a bright hope of a glorious destiny hereafter? Away with the word in such a view and with such a thought! It is emphatically no sacrifice. Say rather it is a privilege. Anxiety, sickness, suffering, or danger now and then with a foregoing of the common conveniences and charities of this life, may make us pause and cause the spirit to waver and the soul to sink; but let this only be for a moment. All these are nothing when compared with the glory which shall be revealed in and for us. I never made a sacrifice.

Source: Of Human Bondage (1915), Ch. 51

Source: The Laundry Files, The Labyrinth Index (2018), Chapter 10, “Flight Plan” (p. 296)