Address at the Sorbonne, Paris, 23 Apr. 1910. Richard M. Nixon quoted this passage in his address to the nation announcing his decision to resign the presidency, 8 Aug. 1974. See Theodore Roosevelt 1; Theodore Roosevelt 2; Theodore Roosevelt 5
Mike Krzyzewski, Donald T. Phillips (2010). “Leading with the Heart: Coach K's Successful Strategies for Basketball, Business, and Life”, p.52, Hachette UK