Several years ago, my dentist noted that my teeth were showing signs of wear that suggested grinding during sleep, or some other tension-related response.
Yesterday, I had an emergency visit to my dentist - my symptoms was pain when chewing. After an extensive series of x-rays and tests, the dentist concluded that my problem was not a tooth/dental problem, but rather TMJ - a problem that can be caused by a number of factors including grinding of the teeth and tension. His suggestion was to shift to a diet of softer foods for a week, combined with ibuprophen.
So the point is that this is a real concern, and intense focus creates stress that can have painful consequences.
Intellectually, I know that my best turning results from being relaxed about what I'm doing. But like many others, I often find myself focusing very hard to what I'm doing, and tensing up in a way that I know doesn't produce the best results. And my dentist would add that it's not healthy. And my credit card says that the cost of treatment isn't cheap.