“Either don't try at all or make damned sure you succeed.”
Book I, line 389 (tr. James Michie)
Ars Amatoria (The Art of Love)
Original
Aut non rem temptes aut perfice.
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Ovid 120
Roman poet -43–17 BCRelated quotes

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

“Avoid this crowd like the plague. And if they quote you, make damn sure they heard you.”
Advice about news reporters, to incoming first lady, Hillary Rodham Clinton, on a tour of the White House, as quoted in Newsweek magazine (30 November 1992)
Brazil v. Germany (8 July 2014).
2010s, 2014, 2014 FIFA World Cup
Context: Lahm, Khedira. Lahm, again. Trying to make sure, and they do make sure! Six, nil! You wonder where all this is going to end for Germany? Schürrle, getting in on the act. Well, they're really booing now. André Schürrle. Fred was booed off in the middle of all that. And Schürrle gets his second goal of the tournament, he got one against Algeria as well. Six, nil. Germany, really rubbing Brazil's noses in it.

“I will try to develop an entirely new style and I am sure I will succeed.”