In 'Real Simple' (a magazine I admittedly don't read for substance), just today:

Drop Your Jaw

If I feel my body tensing up, I relax my jaw, tongue, and larynx, which helps catalyze calm, says Boris Dubrovsky, PhD, a psychologist at New York-Presbyterian Brooklyn Methodist Hospital. "When we have racing, anxious thoughts, we tend to subvocalize, creating a constant internal monologue that engages all these muscles even without speech production," he explains. "Relaxing those muscles disrupts the feedback loop, and your thoughts stop midair." Several times a day, whenever I notice my jaw clenching, I open my mouth wide and let my lax tongue hang out for 30 to 60 seconds.

I've read previously that consciously relaxing three tension points - loosening the spot between the brows; dropping tongue off the roof of the mouth; and unclenching tight stomach muscles, all symptomatic of the 'fight' response - does momentarily return the body to a stay of self-awareness, and found it generally to be true. The sentence above, however, re: 'subvocalizing', is a brilliant observation. I do need help stopping my inner monologue (and occasionally playing out both sides of a mental dialogue).