A few from those collected over the years:
"Skepticism is the chastity of the intellect, and it is shameful to surrender it too soon or to the first comer." (George Santayana)
"When you come to the end of your life, make sure that you are used up." (attributed to Turgenev)
"It is the final proof of God's omnimipotence that he need not exist in order to save us." (Peter de Vries)
"Interpretation is the revenge of the intellect upon art." (Susan Sontag)
"It's a fatal thing to take literature and art too seriously if you lack judgment." (Richard Aldington)
"The average man, who does not know what to do with his life, wants another one which lasts forever." (Anatole France)
"Pride is a good chest protector but a bad bicycle." (Joyce Cary as Gully Jimson)
"In the fight between you and the world, back the world." (Kafka)
"Beware of the man who works hard to learn something, learns it, and finds himself no wiser than before. He is full of murderous resentment of people who are ignorant without having come by their ignorance the hard way." (Kurt Vonnegut as Bokonon)
"It is probably all right to try to be anything you cannot be, when you find that you cannot be everything that you are." (Walt Kelly)
"Virtue is to be feared more than vice, because its excesses are not subject to the regulations of conscience." (Albert Jay Nock)
"If you see a blind man, kick him - why should you be kinder than God?" (Arabic proverb)