What kind of habits do you have that are hurting your teeth/mouth? Obviously, smoking and chewing tobacco can lead to oral cancer. But, what about habits that might not be as obvious?
1) Hard Candy / Cough Drops - Many of these products are not sugar free, and may even boast that they contain enough vitamin C for an army. Avoid chomping right into them as this can cause a tooth to fracture, but also avoid consuming one right after the other. The sugar in these products can sit on your teeth, and cause cavities. Worse, watch out for anything citrus flavored as it likely contains lots of citric acid which will quickly demineralize tooth enamel making it easy for cavities to form.
2) Energy Drinks - Looking to get over that afternoon slump? Stay away from energy drinks! The combination of sugar, citric acid, and carbonic acid make quick work of tooth enamel. And, please, don't run and brush your teeth right away. You could easily brush away that softened enamel. Instead, have a glass of water and wait at least thirty minutes.
3) Using Teeth as Tools - Your teeth are designed to be functional when they are chewing food, not opening beer bottles. Nor should they be used to cut tags off of clothing, cut fishing line, or open plastic bags. Your could break a tooth, or gash open your gums.