“Do not burden yourself with problems that you do not understand,’ he said. ‘If you do, then only the problems win. Human life becomes a tragedy.”

Source: In The Face of Danger

From Discover the Champion in You, pages 70

Interview to Cosmopolitan (2016)

Variant translations
If you know others and know yourself, you will not be imperiled in a hundred battles; if you do not know others but know yourself, you win one and lose one; if you do not know others and do not know yourself, you will be imperiled in every single battle.
Know your enemy and know yourself, find naught in fear for 100 battles. Know yourself but not your enemy, find level of loss and victory. Know not thy enemy nor yourself, wallow in defeat every time.
Literal translation: Know [the] other, know [the] self, hundred battles without danger; not knowing [the] other but know [the] self, one win one loss; not knowing [the] other, not knowing [the] self, every battle must [be] lost.
Source: The Art of War, Chapter III · Strategic Attack

Source: Dear Ijeawele, or A Feminist Manifesto in Fifteen Suggestions

Stopped in Our Tracks, Book Two: Excerpts from U.G.'s Dialogues (2005) by K. Chandrasekhar

Original in French: Comprenez-vous maintenant le lien qui existe entre la question des générations spontanées et ces grands problèmes que j'ai énumérés en commençant? Mais, messieurs, dans un pareil sujet, assez de poésie comme cela, assez de fantaisie et de solutions instinctives; il est temps que la science, la vraie méthode reprenne ses droits et les exerce. Il n'y a ici ni religion, ni philosophie, ni athéisme, ni matérialisme, ni spiritualisme qui tienne. Je pourrais même ajouter : Comme savant, peu m'importe. C'est une question de fait; je l'ai abordée sans idée préconçue, aussi prêt à déclarer, si l'expérience m'en avait imposé l'aveu, qu'il existe des générations spontanées, que je suis persuadé aujourd'hui que ceux qui les affirment ont un bandeau sur les veux.
Also found in Histoire du développement de la biologie, Volume 3, by Hendrik Cornelius Dirk de Wit (1994), PPUR presses polytechniques, p. 393
Soirées scientifiques de la Sorbonne (1864)
Context: Do you understand now the relationship between the question of spontaneous generation and the major problems that I listed in the beginning? But, gentlemen, in such a subject, rather than as poetry, pretty fancy and instinctive solutions, it is time for science, the true method resumes its duties and exercise. Here, it takes no religion, no philosophy, no atheism, no materialism, no spiritualism. I might even add: as a scholar, I do not mind. It is a matter of fact; I approached without a preconceived idea, too ready to declare, if the experiment had imposed upon me the confession, that there was a spontaneous generation, of which I am convinced today that those who assure it are blindfolded.

Source: Music is My Mistress

Introduction to Treasury of the Free World (1946)