One I like currently is from Torchwood, Miracle Day: The Blood Line.
"The future can change. It's being written right now. But one thing I do know, I've seen the stars. I have seen the universe. I have seen the human race become vast, magnificent and endless. And I wish you could see it, Oswald. I wish you could see that too. 'Cause then you'd know how small you've made your life."
-Captain Jack Harkness
Or possibly a Doctor Who quote. There are just too many for me to actually pick one.