“Only God knows the beginning and the end.”

Source: Dear John

Thoughts and Aphorisms (1913), Karma
Context: If thou think defeat is the end of thee, then go not forth to fight, even though thou be the stronger. For Fate is not purchased by any man nor is Power bound over to her possessors. But defeat is not the end, it is only a gate or a beginning.

Fellini on Fellini (1976) edited by Anna Keel and Christian Strich; translated by Isabel Quigly.
Variant: There is no end. There is no beginning. There is only the passion of life.

Source: De Profundis

Mountain Interval (1920), 5. In the Home Stretch, Line 187-192
General sources
Context: “My dear,
It’s who first thought the thought. You’re searching, Joe,
For things that don’t exist; I mean beginnings.
Ends and beginnings—there are no such things.
There are only middles.

Comments to Prof. David F. Boyd at the Louisiana State Seminary (24 December 1860), as quoted in The Civil War : A Book of Quotations (2004) by Robert Blaisdell. Also quoted in The Civil War: A Narrative (1986) by Shelby Foote, p. 58.
1860s, 1860
Context: You people of the South don't know what you are doing. This country will be drenched in blood, and God only knows how it will end. It is all folly, madness, a crime against civilization! You people speak so lightly of war; you don't know what you're talking about. War is a terrible thing! You mistake, too, the people of the North. They are a peaceable people but an earnest people, and they will fight, too. They are not going to let this country be destroyed without a mighty effort to save it … Besides, where are your men and appliances of war to contend against them? The North can make a steam engine, locomotive, or railway car; hardly a yard of cloth or pair of shoes can you make. You are rushing into war with one of the most powerful, ingeniously mechanical, and determined people on Earth — right at your doors. You are bound to fail. Only in your spirit and determination are you prepared for war. In all else you are totally unprepared, with a bad cause to start with. At first you will make headway, but as your limited resources begin to fail, shut out from the markets of Europe as you will be, your cause will begin to wane. If your people will but stop and think, they must see in the end that you will surely fail.

Review of Nausea by Jean-Paul Sartre, published in the newspaper Alger Républicain (20 October 1938), p. 5; also quoted in Albert Camus and the Philosophy of the Absurd (2002) by Avi Sagi, p. 43
Context: It is the failing of a certain literature to believe that life is tragic because it is wretched.
Life can be magnificent and overwhelming — that is its whole tragedy. Without beauty, love, or danger it would be almost easy to live. And M. Sartre's hero does not perhaps give us the real meaning of his anguish when he insists on those aspects of man he finds repugnant, instead of basing his reasons for despair on certain of man's signs of greatness.
The realization that life is absurd cannot be an end, but only a beginning. This is a truth nearly all great minds have taken as their starting point. It is not this discovery that is interesting, but the consequences and rules of action drawn from it.

Inaugural Address (2003)