The best option is to reduce stress. However, that is sometimes easier said than done. The easiest thing to do is to have a nightguard produced. Additionally, a massage therapy, heat treatment and even autogenic training, yoga and Tai Chi can help to reduce nocturnal teeth grinding and the symptoms of bruxism.
If teeth grinding has been reducing the tooth substance significantly you can re-establish the anatomy of the teeth with composite fillings (this is a more temporary option) or full ceramic partial crowns (so-called tabletops).