“I hope it is true that a man can die and yet not only live in others but give them life, and not only life but that great consciousness of life.”

Source: Costly Grace, p. 45.
Context: Costly grace is the gospel which must be sought again and again, the gift which must be asked for, the door at which a man must knock.
Such grace is costly because it calls us to follow, and it is grace because it calls us to follow Jesus Christ. It is costly because it costs a man his life, and it is grace because it gives a man the only true life. It is costly because it condemns sin, and grace because it justifies the sinner.

Source: The Magic Mountain (1924), Ch. 2, “At Tienappels’,” (1924), trans. by H.T. Lowe-Porter (1928).

Source: Attributed in posthumous publications, Einstein and the Poet (1983), p. 91

In answer to a question asked by the editors of Youth, a journal of Young Israel of Williamsburg, NY. Quoted in the New York Times, June 20, 1932, pg. 17 http://select.nytimes.com/gst/abstract.html?res=F40617F83B5A13738DDDA90A94DE405B828FF1D3
Unsourced variant: Only a life in the service of others is worth living.
1930s
Variant: I believe in one thing—that only a life lived for others is a life worth living.

Source: Life of Pi (2001), Chapter 56, p. 178

Source: The Collected Poetry, 1968-1998

Sacrifice https://www.marxists.org/archive/guyau/1895/sacrifice.htm, Pages Choisies des Grands Écrivains (1895).
Context: We can judge ourselves and our ideal by posing this question: For what idea, for what person would I be ready to risk my life? He who cannot answer such a question has a vulgar and empty heart. He is incapable of feeling or doing anything grand in life, since he is unable to go beyond his individuality. He is impotent and sterile, dragging along his selfish ego like the tortoise its shell. On the contrary, he who has present in his spirit the idea of death for his ideal seeks to maintain this ideal at the height of this possible sacrifice. He draws from this supreme risk a constant tension and an indefatigable energy of the will. The only means of being great in life is having the consciousness that you will not retreat before death.

Source: His Dark Materials, The Amber Spyglass (2000), Ch. 26 : The Abyss
Context: Your dæmon can only live its full life in the world it was born in. Elsewhere it will eventually sicken and die. We can travel, if there are openings into other worlds, but we can only live in our own. Lord Asriel’s great enterprise will fail in the end for the same reason: we have to build the Republic of Heaven where we are, because for us there is no elsewhere.