I changed dentists after moving a couple years ago. My new dentist said I grind my teeth and need to make a mental note before going to sleep to not clinch and grind my teeth. I said "I used to grind my teeth when I was a little kid, but haven't in many years". He lined up my teeth and showed me the wear from the grinding and said the opposite that I had been grinding my teeth for years.
I wore a soft guard like that and found it to be an uncomfortable POS. I had a hard one custom made and it felt like a tight retainer at first, but once I got used to it, worked great. After a few months I didnt need it anymore. Just telling myself mentally "no clinching and no grinding" a few times before sleep trained my brain. If I did clinch or grind after that, I would wake up and stop.
I still do wear my mouthguard now and then if I cant sleep. For some reason I still associate it with "time to go to sleep" so if I cant fall asleep I put in the mouthguard and lights out...
Sorry, long story.. You might be normal though.
Its not always stress and just telling yourself to not clinch or grind your teeth before sleep can do wonders. Almost a meditation type thing that sticks with your subconscience.