“If at Last You Do Succeed, Never Try Again.”
"—All You Zombies—" (1958)
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Robert A. Heinlein 557
American science fiction author 1907–1988Related quotes
“That's why I love spiders. 'If at first you don't succeed, try, try, try again.”
Source: Howl's Moving Castle

“When I was a little boy I used to repeat: "If at first you don't succeed, try, try, try again."”
That is what I am doing. When I come back I hope I may be able to say, as Hotspur said in Henry IV, "Out of this nettle, danger, we pluck this flower, safety."
Speech at Heston Airport before his flight to Munich to meet Hitler (29 September 1938), quoted in The Times (30 September 1938), p. 12
Prime Minister

“Never try to discourage thinking, for you are sure to succeed.”

“Do not try to live for ever. You will not succeed.”
Preface
1910s, The Doctor's Dilemma (1911)

“If we fail, let us try again and again until we succeed.”
As a response to Prime Minister Gladstone's criticism of Chamberlain's "Radical Programme," from a Speech at Warrington, cited in "Great Issues in Western Civilization, Volume II" (Donald Kagan, 1992), pg. 419.
1880s

“They are trying to make an elder statesmen of me, but they will never succeed.”
Mr. Citizen, Harry Truman (1960)
Context: Student: Some people suggest that you are getting mellowed and less militant. Is that so?
Truman: Not in the slightest degree. They are trying to make an elder statesmen of me, but they will never succeed.
Interview with the Fiji Times http://www.Fijitimes.com, 25 September 2005 (excerpts)