When you clench or teeth together or grind them together this is referred to as Bruxism. Many people are not aware that they doing this and might be brought on by stress or anxiety. Sleep-related bruxism is much harder to control.
Grinding can wear down your teeth and cause deterioration. Your jaw muscles can get sour from the pressure on the muscle tissue. Some ear pain or infection can be a result of Bruxism.
The treatment is to try to relax more. In severe cases a mouth guard or splint appliance can be used to keep the teeth from being damaged more.