Remember, no one came to see you fail. Convince yourself that there are no enemies in the room, and, the same door that let them in will allow them to leave if they don't like what they see.

personally, I like hecklers; as long as I have the mike I can make a fool out of them, and usually, that is not too hard to do.

Try to make contact with them on a personal basis, most people like entertainers better than performers.