Grinding your teeth
A common misconception is that everyone grinds their teeth due to stress. The reality is that there is a problem with your bite. Your upper and lower jaws fit together like a lock and key. If they don't fit together when you bite, it puts uneven stress on your jaw muscles. Then the jaw muscles will try to find an balanced, comfortable position, which often will result in grinding teeth down until they are flat. It may take years to grind teeth flat, but the damage is irreversible. It is essentially similar to losing tooth structure from a cavity, except in this case it is not caused by bacteria.