“There’s only one way to succeed in anything, and that is to give it everything. I do, and I demand that my players do. ”
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Vince Lombardi 33
American football player, coach, and executive 1913–1970Related quotes

To his penitents. Quoted in "An important anniversary to celebrate", The Malta Independent (20 August 2017) http://www.independent.com.mt/articles/2017-08-20/newspaper-letters/An-important-anniversary-to-celebrate-6736177986.

Edward Everett Hale in a statement published in A Year of Beautiful Thoughts (1902) by Jeanie Ashley Bates Greenough, p. 172; <!-- and perhaps as early as an edition of Ten Times One is Ten (1870) by Hale--> This has been misattributed to Keller in published works since at least 1980. Keller and Hale were good friends, and letters to Hale can be found in her youthful autobiography The Story of My Life (1902). In 1910 Keller dedicated her poem "The Song of the Stone Wall" to Hale who had died in 1909.
Misattributed
Variant: I am only one, but I am one. I can not do everything, but I can do something. I must not fail to do the something that I can do.

Statement published in A Year of Beautiful Thoughts (1902) by Jeanie Ashley Bates Greenough, p. 172, Third statement for June 11. This has often been misattributed to Helen Keller in some published works since at least 1980, perhaps because she somewhere quoted it.
Variant:
I am only one,
But still I am one.
I cannot do everything,
But still I can do something;
And because I cannot do everything,
I will not refuse to do the something that I can do.
The Book of Good Cheer : A Little Bundle of Cheery Thoughts (1909) by Edwin Osgood Grover, p. 28; also in Masterpieces of Religious Verse (1948) by James Dalton Morrison, p. 416, where it is titled "Lend a Hand"
Variant: I am only one, but still I am one. I cannot do everything, but still I can do something; and because I cannot do everything, I will not refuse to do something that I can do.

“I can DO ANYTHING I want, but I can't DO EVERYTHING I want.”
Source: The Happiness Project: Or Why I Spent a Year Trying to Sing in the Morning, Clean My Closets, Fight Right, Read Aristotle, and Generally Have More Fun

Statement published in A Year of Beautiful Thoughts (1902) by Jeanie Ashley Bates Greenough, p. 172, Third statement for June 11. This has often been misattributed to Helen Keller in some published works since at least 1980, perhaps because she somewhere quoted it.
Variant:
I am only one,
But still I am one.
I cannot do everything,
But still I can do something;
And because I cannot do everything,
I will not refuse to do the something that I can do.
The Book of Good Cheer : A Little Bundle of Cheery Thoughts (1909) by Edwin Osgood Grover, p. 28; also in Masterpieces of Religious Verse (1948) by James Dalton Morrison, p. 416, where it is titled "Lend a Hand"

USA Today 2005-08-02.

“Everything I do and say and the way I do and say it annoys me.”
As quoted in "William F. Buckley Jr., Rapier Wit Of the Right" in The Washington Post (28 February 2008) http://www.washingtonpost.com/wp-dyn/content/article/2008/02/27/AR2008022703901.html.