“This above all, to refuse to be a victim. Unless I can do that I can do nothing.”

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.

Source: Be Here Now

Source: The Song of Achilles

Song lyrics, The Dreaming (1982)
Context: Out in the garden
There's half of a heaven,
And we're only bluffing.
We're not ones for busting through walls,
But they've told us
Unless we can prove
That we're doing it,
We can't have it all.

Coffee, Please!
How to Be a Hermit (1929)

1900s, A Square Deal (1903)
Context: Among ourselves we differ in many qualities of body, head, and heart; we are unequally developed, mentally as well as physically. But each of us has the right to ask that he shall be protected from wrong-doing as he does his work and carries his burden through life. No man needs sympathy because he has to work, because he has a burden to carry. Far and away the best prize that life offers is the chance to work hard at work worth doing; and this is a prize open to every man, for there can be no better worth doing than that done to keep in health and comfort and with reasonable advantages those immediately dependent upon the husband, the father, or the son. There is no room in our healthy American life for the mere idler, for the man or the woman whose object it is throughout life to shirk the duties which life ought to bring. Life can mean nothing worth meaning, unless its prime aim is the doing of duty, the achievement of results worth achieving.