“That was when she recognized love: this torture on seeing someone, the greater torture when he was out of sight, in short, a torture without end.”

Source: Diary

Source: I'd Tell You I Love You, But Then I'd Have to Kill You

The monster to Robert Walton in Ch. 24
Frankenstein (1818)

L’amour ressemblait fort à une torture ou à une opération chirurgicale.
III http://fr.wikisource.org/wiki/Fus%C3%A9es#III
Journaux intimes (1864–1867; published 1887), Fusées (1867)

Source: The Bloody Chamber and Other Stories

Kelly (1969) in interview with William B. Arthur. Cited in: James Spada (1988) Grace: The Secret Lives of a Princess. p. 280

Variant: There are so many torturous things in this life. Don't let a man who doesn't love you be one of them.
Source: Tiny Beautiful Things: Advice on Love and Life from Dear Sugar

"Life Ahead: On Learning and the Search for Meaning" (1963), Introduction http://www.jkrishnamurti.com/krishnamurti-teachings/view-text.php?tid=38&chid=331, J.Krishnamurti Online, JKO Serial No. 261, p. 13, 2005 edition
1960s
Context: Learning in the true sense of the word is possible only in that state of attention, in which there is no outer or inner compulsion. Right thinking can come about only when the mind is not enslaved by tradition and memory. It is attention that allows silence to come upon the mind, which is the opening of the door to creation. That is why attention is of the highest importance. Knowledge is necessary at the functional level as a means of cultivating the mind, and not as an end in itself. We are concerned, not with the development of just one capacity, such as that of a mathematician, or a scientist, or a musician, but with the total development of the student as a human being. How is the state of attention to be brought about? It cannot be cultivated through persuasion, comparison, reward or punishment, all of which are forms of coercion. The elimination of fear is the beginning of attention. Fear must exist as long as there is an urge to be or to become, which is the pursuit of success, with all its frustrations and tortuous contradictions. You can teach concentration, but attention cannot be taught just as you cannot possibly teach freedom from fear; but we can begin to discover the causes that produce fear, and in understanding these causes there is the elimination of fear. So attention arises spontaneously when around the student there is an atmosphere of well-being, when he has the feeling of being secure, of being at ease, and is aware of the disinterested action that comes with love. Love does not compare, and so the envy and torture of "becoming" cease.