I don't know anything about this particular ailment. But look at the literature for fixing your posture. That also involves changing what your body is doing at

I don't know anything about this particular ailment. But look at the literature for fixing your posture. That also involves changing what your body is doing at rest while you are not paying attention. Some of the principles involved in changing your posture (often involving which muscles are kept relaxed and which stretched) might very well apply to helping you relax your jaw muscles.