“I gave up what I can't keep for something I can never lose.”

Source: Henry & June

Source: Ghost Town

Joyce's reply for a request for a plan of Ulysses, as quoted in James Joyce (1959) by Richard Ellmann

Turning Tables, written by Adele and Ryan Tedder.
Song lyrics, 21 (2011)

Crocodile Rock
Song lyrics, Don't Shoot Me I'm Only the Piano Player (1973)

As quoted in "The Rides of Passage" in Via magazine (July 2005)
Context: Disneyland is something that will never be finished. It's something that I can keep developing. It will be a live, breathing thing that will need change. A picture is a thing, once you wrap it up and turn it over to Technicolor, you're through. Snow White is a dead issue with me. But I can change the park, because it's alive.

Year unknown, published in 2001, The Quotable Walt Disney (2001)

Source: Life Doesn't Frighten Me

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"