Relax, it is not that serious.
Have you ever seen runners and walkers coming towards you and everything is clenched up. They've locked their jaws, their neck. Their eyes are straight-forward, they've got a scowl on their face. It looks painful, well guess what, it is.
When they stop, all those tight muscles are screaming for relief.
The best way to run or walk is to try to hold your arms loosely at a 90-degree angle, bend at your waist, let your jaw slack. If you're drooling, you're probably a little bit too slack.
Just relax, this is supposed to be fun for the most part even though you don't.