I do this when I get stressed. Shoulders too. I have to consciously check in throughout the day (pretty much only when I'm working a shift at the hospital) to make sure I'm relaxing those areas. My new watch has actually been helping a lot. It's wildly accurate at picking up when Im stressed, usually before I even realize I'm getting stressed. Could be totally irrelevant for you but it's worth trying if you don't know what's causing the clenching (some people do it in their sleep)