I have pretty much always done this, especially in times of stress. It has resulted in cracked teeth and terrible tension headaches. I have been through various mouth guards and the dentist ended up telling me to stop using them as I was biting them too much, and to find other ways of dealing with the issue.
I'm back in the middle of a stressful period and have had a headache for a week now, and sore areas in my neck and throat. I stop myself from doing it when I catch myself doing it while awake, but it does take a while for me to realise I am doing it - and that doesn't happen when I am asleep.
Has anyone successfully overcome this without using a mouth guard?