Not to get all religious on you, but here's something to ponder: The other night, while Michael and I were playing for Shabbat services, the F natural on my D string started buzzing. He was worried that there might be something wrong with my instrument, but I assured him that the problem probably had something to do with my bow arm, since it was a stopped note and not an open string. Oddly, a similar thing happened at the last Shabbat service, but it never seemed to happen in my normal practice (in normal-to dead acoustics).
The first thing Saturday morning I tried to figure out what the problem could be, and then I realized that it had something to do with the position of my upper arm relative to the timing of the string crossing. It took me a few enlightening hours of practicing Kreutzer and Bach to fix the problem, but I fixed the problem, and it made all sorts of improvements in my playing (and in good time too, since I had a concert to play today).
If this problem hadn't occurred in shul, I might not have noticed it, and therefore I wouldn't have fixed it. Hmm.