I've had problems with bruxism for decades. Dentist said it was stress, he gave me a mouthguard and I proceeded to break it. I would still grind my teeth even if I was super relaxed.

I now do something that has reduced my bruxism by a LOT:

Mouth taping.

My dad's old college roommate is a bruxism expert and wrote to me:

"Bruxism is the body's attempt to dilate pharyngeal muscles to open the airway and facilitate breathing. You probably snore and or have sleep apnea."

Mouth taping solves this because it forces my body to breath thru the nose vs the mouth and consequently I get more oxygen and much better sleep.

Add a magnesium supplement to this and I'm doing so much better.

EDIT: Forgot to mention I had bad allergies and have asthma so I learned bad breathing habits early on. AKA mouth breathing.

A simple test: Where is your tongue resting right now? If it's at the bottom of your mouth, you're probably a mouth breather. And that's not good!