“The brave man is not the one without fear but the one who does what he must despite being afraid. To succeed, you must be willing to risk total failure; you must learn this.”

Lectures XIV and XV, "The Value of Saintliness"
1900s, The Varieties of Religious Experience (1902)

Source: The Final Empire

Variant: How does one become a butterfly? They have to want to learn to fly so much that you are willing to give up being a caterpillar.
Source: Hope for the Flowers

Conclusion
The Ethics of Ambiguity (1947)
Context: A conquest of this kind is never finished; the contingency remains, and, so that he may assert his will, man is even obliged to stir up in the world the outrage he does not want. But this element of failure is a very condition of his life; one can never dream of eliminating it without immediately dreaming of death. This does not mean that one should consent to failure, but rather one must consent to struggle against it without respite.

Variant: The moment people come to know love, they run the risk of carrying hate.

Quiet Strength (2000)

Address http://www.ted.com/talks/james_cameron_before_avatar_a_curious_boy.html/ to the 2010 TED conference (13 February 2010)
Context: Imagination is a force that can actually manifest a reality. … Don’t put limitations on yourself. Other people will do that for you. Don’t do that to yourself. Don’t bet against yourself. And take risk. NASA has this phrase that they like, "Failure is not an option." But failure has to be an option. In art and exploration, failure has to be an option. Because it is a leap of faith. And no important endeavour that required innovation was done without risk. You have to be willing to take those risks. … In whatever you are doing, failure is an option. But fear is not.

UN Press Release SG/360 (22 December 1953)
Context: Our work for peace must begin within the private world of each one of us. To build for man a world without fear, we must be without fear. To build a world of justice, we must be just. And how can we fight for liberty if we are not free in our own minds? How can we ask others to sacrifice if we are not ready to do so?... Only in true surrender to the interest of all can we reach that strength and independence, that unity of purpose, that equity of judgment which are necessary if we are to measure up to our duty to the future, as men of a generation to whom the chance was given to build in time a world of peace.