A man who knows a subject thoroughly, a man so soaked in it that he eats it, sleeps it and dreams it -- this man can almost always teach it with success, no matter how little he knows of technical pedagogy. That is because there is enthusiasm in him, and because enthusiasm is as contagious as fear or the barber's itch...
I'm not one to snag an entire post, so click on the link to read the full post. It reminds me of a quote by Henry Chester that is on my bathroom mirror:
Enthusiasm is the greatest asset in the world. It beats money and power and influence. It is no more or less than faith in action.
If you don't have enthusiasm for what you do, why are you doing it?