The Ancient Greeks believed that yawning was not a sign of boredom, but that a person's soul was trying to escape from its body, so that it may rest with the gods in the skies. - Wikipedia
Yawning may not be harmful to the soul, but in my case it's bad for the jaw. I've had TMJ for as long as I can remember and usually it doesn't bother me. I'm careful when I yawn and I gave up jawbreakers and gobstoppers years ago, but sometime during the night on Sunday, I yawned and heard that unpleasant crack of my jaw joints and now I'm in pain.
On top of that, I think one of my fillings is broken. I only have a few fillings, but one of them was feeling a bit strange during lunch, so today I have to go to the dentist. I don't know how I'm going to get my mouth open wide enough for him to look at my tooth - I could barely take a bite of my sandwich.
If it isn't one thing, it's another, and sometimes it's two things at once. And most of time everything happens just whem I'm sitting down to write.