Bruce had me up to three miles a day, really at a good pace. We'd run the three miles in twenty-one or twenty-two minutes.
Then, one day, he said "We're going to go for five. When we get to three, we'll shift gears, it's only two more."
I said "Okay". Into the fourth mile I'm okay for three or four minutes, and then I really begin to give out. I'm tired, my heart's pounding, and so I say to him, "Bruce if I run any more I'm liable to have a heart attack and die."
He said, "Then die." It made me so mad that I went the full five miles. Later I asked him, "Why did you say that?"
He said, "Because you might as well be dead. If you always put limits on what you can do, it'll spread over into the rest of your life. It'll spread into your work, into your entire being. There are no limits. There are plateaus, but you must not stay there, you must go beyond them. If it kills you, it kills you. A man must constantly exceed his level."
~ Bruce Lee, John Little
(The Art of Expressing the Human Body)
The only way to discover the limits of the possible is to go beyond them into the impossible.
~ Arthur C Clarke