Recently I decided I've had enough of that, and felt it was time to learn how to fix it.
I asked my friend Sandra at Free-from-stress.com any tips she has on relaxing our jaws.
1. Keep reminding yourself to do a jaw scan - asking yourself if your jaw is relaxed every now and again.
2. Keep a half smile: you can't tense your jaw when you half-smile.
3. Take the tip of your tongue, and rest it just behind your top teeth. Get used to doing it and do it lots. It's another one where you can't tense your jaw if your tongue is in this position.
There are a few more things I've found we can do to try and relieve jaw tension. Usually there is a bad habit that is contributing to hurty jaws, such as an insatiable pen-nibbling habit, chewing food super thoroughly, grinding your teeth, keeping time to the music with your teeth (I do this), gum chewing, and shitty posture - having your head forward of your spine like a turkey vulture puts tension in your jaws, so sit up straight y'all. Figure out out if you have one of these bad habits, and start trying to catch yourself doing it
Another jaw exercise I've found for releasing the muscle where the jaw bone joins the spine next to your ears (this guy's called the Temporomandibular Joint and it's the bit that sometimes can feel all clicky and crunchy when you open and close your mouth) is putting your thumb on your chin and putting a slight bit of pressure up, so you are gently pushing your chin up into your face. Nice and slow, open your mouth all the way and close it around 10 times, using your thumb to gently offer resistance.
I also find a trip to the osteopath to click and evil-pain-massage out all the crap in my neck and shoulders really helps relieve my stressed face. Body bits love bothering their neighbours, so if you have knotted up shoulders, chance is they are trying to tell your neck and jaw about it and get them involved. My osteo lives here - his name is Mojo, he is a bit intense but he is excellent.