I live by a hill. I began walking it and then I began jogging it and then I began sprinting it.
Some think guts is sprinting at the end of a race. But guts is what got you there to begin with. Guts start back in the hills with 6 miles to go and you're thinking of how you can get out of this race without anyone noticing. Guts begin when you still have forty minutes of torture left and you're already hurting more than you ever remember.
Think of it this way: performing is like sprinting while screaming for three, four minutes. And then you do it again. And then you do it again. And then you walk a little, shouting the whole time. And so on. Your adrenaline quickly overwhelms your conditioning.
I entered the film industry sprinting, but not for long.