“Man seeks to escape himself in myth, and does so by any means at his disposal. Drugs, alcohol, or lies. Unable to withdraw into himself, he disguises himself. Lies and inaccuracy give him a few moments of comfort.”

Niebla [Mist] (1914)
Context: Whenever a man talks he lies, and so far as he talks to himself — that is to say, so far as he thinks, knowing that he thinks — he lies to himself. The only truth in human life is that which is physiological. Speech — this thing that they call a social product — was made for lying.

Variant translations:
Above all, do not lie to yourself. A man who lies to himself and listens to his own lie comes to a point where he does not discern any truth either in himself or anywhere around him, and thus falls into disrespect towards himself and others. Not respecting anyone, he ceases to love, and having no love, he gives himself up to passions and coarse pleasures, in order to occupy and amuse himself, and in his vices reaches complete bestiality, and it all comes from lying continually to others and to himself. A man who lies to himself is often the first to take offense. It sometimes feels very good to take offense, doesn't it? And surely he knows that no one has offended him, and that he himself has invented the offense and told lies just for the beauty of it, that he has exaggerated for the sake of effect, that he has picked on a word and made a mountain out of a pea — he knows all of that, and still he is the first to take offense, he likes feeling offended, it gives him great pleasure, and thus he reaches the point of real hostility… Do get up from your knees and sit down, I beg you, these posturings are false, too.
Part I, Book I: A Nice Little Family, Ch. 2 : The Old Buffoon; as translated by Richard Pevear and Larissa Volokhonsky, p. 44
The Brothers Karamazov (1879–1880)

Ez ist ein armer trügesite,
der vriunden alsô liuget,
daz er sich selben triuget.
Source: Tristan, Line 12308

The Analects, Chapter I

"Myth on the Right," in Mythologies (1957)

This Business of Living (1935-1950)

The trial of Charles B. Reynolds for blasphemy (1887)
Context: Religions are for a day. They are the clouds. Humanity is the eternal blue. Religions are the waves of the sea. These waves depend upon the force and direction of the wind -- that is to say, of passion; but Humanity is the great sea. And so our religions change from day to day, and it is a blessed thing that they do. Why? Because we grow, and we are getting a little more civilized every day, -- and any man that is not willing to let another man express his opinion, is not a civilized man, and you know it. Any man that does not give to everybody else the rights he claims for himself, is not an honest man.

Source: The Gate of Worlds (1967), Chapter 9 “To the Western Sea” (p. 162)

Telling the Truth (1977)
Source: Telling the Truth: The Gospel as Tragedy, Comedy, and Fairy Tale