Yes, this can be an issue. I used to have a lot of problems with it as well.

If you clench or grind during the day, you can train yourself out of it. I used to have trouble with that. I have had a lot of trouble with my jaw joints, and I went to a clinic for treatment at a local university's dental school. They taught various exercises to relax the jaw, and also a helpful routine. Memorize this idea, "Lips together, teeth apart." Keeping your mouth that way is the easiest on your jaw. Keep checking yourself throughout the day, and make sure that you are following that idea - lips together, teeth apart. You can set a timer to remind yourself for the first week or so when you are at home (every 15 minutes or so). You can associate some frequent thing with the phrase to trigger a reminder; say, everytime you are at a traffic light, make it a reminder to check yourself. Are your lips together, and your teeth apart? Every time there is a commercial on television, are your lips together and your teeth apart? You'll get the idea, and start checking and reminding yourself more, and noticing it more often when you are clenching.

Bruxism (teeth grinding) at night is harder to conquer. It's true that you may need to get a guard for that, and it may be necessary to have one specially made. Your dentist may be able to refer you to a specially-trained dentist who can do this, or he may be able to make one himself. It's an investment, but it can help preserve your teeth and your jaw joints in the long run.

Take care,
ErinBear