“The hardest thing I ever did was keep my temper at that time.”
A comment to a personal friend, about Joseph McCarthy's attacks upon his loyalty (which went so far as to call him a "traitor"), as quoted by Alistair Cooke, in Letter from America : General Marshall (16 October 1959), published in Memories of the Great and the Good (1999)
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George Marshall 49
US military leader, Army Chief of Staff 1880–1959Related quotes

Speaking about Joe Namath, the star quarterback, being benched for an infraction before the 1963 final regular-season game against Miami and the Sugar Bowl.
Source: Football's Supercoach, B.J., Phillips, Sep. 29, 1980, Time, 6, 2008-12-11 http://www.time.com/time/magazine/article/0,9171,952802-6,00.html,
pg. 31
Pretty Mess book (2018)

“But the waiting time, my brothers,
Is the hardest time of all.”
Psalms of Life: The Hardest Time of All.

Keynote Speech, SXSW 2006, published in "The wisdom of one" (25 April 2007) http://www.theage.com.au/news/in-depth/the-wisdom-of-one/2007/04/24/1177180647120.html?page=fullpage#contentSwap1

“Staying silent, staying away from him… that was the hardest thing I've ever done.”
Source: The Last Olympian

“It's my rule never to lose me temper till it would be dethrimental to keep it.”
Fluther Good, Act 2
The Plough and the Stars (1926)