“A doctor should never try to cure the incurable.”

7:87
Variant translation: What cannot be cured by medicaments is cured by the knife, what the knife cannot cure is cured with the searing iron, and whatever this cannot cure must be considered incurable.
Aphorisms

Speech (30 April 1954)

Letter to Martha Bernays, after receiving a travel grant he had been having dreams of receiving (20 June 1885)
1880s
Context: Princess, my little Princess,
Oh, how wonderful it will be! I am coming with money and staying a long time and bringing something beautiful for you and then go on to Paris and become a great scholar and then come back to Vienna with a huge, enormous halo, and then we will soon get married, and I will cure all the incurable nervous cases and through you I shall be healthy and I will go on kissing you till you are strong and gay and happy — and "if they haven't died, they are still alive today."

Source: Anna Karenina

"Adventures of Isabel" http://www.poemhunter.com/poem/adventures-of-isabel/

The Soul of Man Under Socialism (1891)
Context: Art is this intense form of individualism that makes the public try to exercise over it an authority that is as immoral as it is ridiculous, and as corrupting as it is contemptible. It is not quite their fault. The public have always, and in every age, been badly brought up. They are continually asking Art to be popular, to please their want of taste, to flatter their absurd vanity, to tell them what they have been told before, to show them what they ought to be tired of seeing, to amuse them when they feel heavy after eating too much, and to distract their thoughts when they are wearied of their own stupidity. Now Art should never try to be popular. The public should try to make itself artistic.

Source: The Greatest Benefit to Mankind: A Medical History of Humanity (1997), p. 14

Source: The Zahir

Source: The Ravishing of Lol Stein