"Space exploration is risky. It's hard. And actually, let me say here that I feel like we need to take on more risk than we have been in space exploration.
"The public doesn't like risk, and they hate failure. But failures happen. They shouldn't happen for stupid reasons. But if they happen when you were trying something risky, you learn. That teaches you something. At least it should. And you try harder next time."
-Lou Friedman, on the failure of the Cosmos-1 solar sailplanetary.org/solarsail blog/index_03.html
"Optimism, pessimism, fuck that; we're going to make it happen. As God is my bloody witness, I'm hell-bent on making it work."
Elon Musk, CEO of Space-X
after failure of the third launch of Falcon-1
interview with Wired
"Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure, than to take rank with those poor spirits who neither enjoy much or suffer much, because they live in the gray twilight that knows not victory nor defeat."
-- Theodore Roosevelt
There are hundreds of good Roosevelt quotes. Some others are here
page by Geoffrey A. Landis, 2008, 2010.