From Peter Elbow’s Writing With Power pg 184:
When listeners really want to hear what we have to say, they seem to suck more words out of us. When listeners are bored or distracted, it is hard to talk clearly and well. And even though larger audiences may seem inherently scary, they sometimes serve to give more support and make talking easier. Most of us have had the experience of three or four friends listening intently to us in such a way that we end up finding more words and being more eloquent than usual. People such as speakers, actors, or teachers who address groups know the peculiar power that can come when an audience is really with you.
It gives a kind of excitement-plus-support that is exhilarating and leads you to find unexpected words and power. Thus most good, experienced performers are not calm and unruffled before performances. They let themselves feel excitement and even anxiety because they know what to do with these emotions. They don’t blot out awareness of the audience; indeed, they probably have more awareness of the audience than a terrified beginner. They come to meet the audience and get the audience to come to meet them, and out of this transaction they build a performance they could not otherwise achieve. By the same token, if you are physically tired or else bored with a topic, an audience can get you up so you can concentrate again and invest yourself in it.
Mark Carrigan 