Honestly, I believe that's where our best writing comes. Mine seems to flow the best when I'm thinking about it the least -- when I'm not aching over every. little. word. that comes. When I'm relaxed and when I fire the little editor-dictator on my shoulder who wants to censor every single word before it hits the keyboard.
In her brilliant book, Bird by Bird, Anne Lamott talks about taking all the little "voices" (the sounds of people in your life who would want you to write a "certain way," or who might criticize what you do, or might even disapprove or make certain suggestions) and turning those voices into mice. Then, she suggests taking those mice, one-by-one by the tail, and dropping them into a big jar. Then, she says, seal the lid (poke holes in it first, of course). Essentially, metaphorically, lock the voices away so that you can have room to be YOU. Room to create without anyone else in the room.
That's basically what Robin Williams did in this scene. He covered the eyes of the painfully-shy Ethan Hawke - because only then could he tune out the other students - their giggles, their jeers, their opinions. And the result was brilliant.
So today, take a moment to relax your creative mind, to shut out all the other distracting voices (even your own!), and sound your barbaric YAWP!