Never use a hard-bristled brush to clean your teeth. Hard bristles can cause gum recession, which can expose delicate root structures of the tooth. The structure of your teeth may begin to show some wear and tear. These factors will combine to give you extremely sensitive teeth. That's why you should use a soft brush (or a medium one at most).
Try your best to stop using tobacco products. Most people are not aware that smoking can cause gum disease, which leads to tooth loss in many. If you want to raise the chances of your teeth lasting much longer, try your best to get rid of your addiction to tobacco products.
If you don't like the taste or texture of toothpaste, consider instead using a paste of baking soda and water. This is a great formula for scrubbing the teeth gently while also leaving a healthy feeling to the mouth. Baking soda is all natural, so it won't cause any problems when you use it.