Here is a solution that will help you not to clench or grind your teeth during the day.
Take the tip of your tongue and touch the roof of your mouth. Now try to clench your teeth. You can't. So this is a "bandaid" effect. Now go to the source of your problem. Why are you so tense? Ask yourself that question and then address the issue. If you don't feel you can address the issue, seek help from someone like a coach or therapist who can.