HERE'S A SUGGESTION:
i have bitten my lip (and even worse, my tongue) far too many times, BUT KNOW THAT EVERY SINGLE TIME I HAVE, it is due to my talking while chewing, or thinking about something else (reading, tv, etc.), or even over-enjoying the food (e.g., chocolate, cookies, etc.) all of which pevent FOCUSING and CONCENTRATING ON THE ACT OF CHEWING. Is this an easy habit to learn ? Maybe not, but EVERY TIME I BEGIN TO EAT, I KNOW I MUST THINK ABOUT THE CONSEQUENCES IF I DON'T (pain and discomfort for many days, inconvenience, worry about possible serious long-term health problems, embarassmemt, regret, feeling stupid, etc.) AND THUS REALIZE IT IS VERY MUCH WORTH IT, AND JUST DO IT. THIS habit (remembering to think about it when i start eating) is NOT so hard to develop, especially because after finishing my meal or snack without incident, i 'REWARD' myself with a mental pat on the back, an imaginary high-five, etc., a 'way to go !'. In fact, i enjoy food even more while concentrating on the act of eating and enjoying it and the act of preventing harm to myself. It feels good (of which i REMIND myself), so i do it !
btw, it is proven that when one eats slowly and concentrates on the food, puts down ones fork and knife and chews well before swallowing, one eats a LOT LESS and thus stays fit. It is also very very important to eat the right foods, and to do this one must think about what one is about to eat, and why, then do it correctly. SO, maybe you have something 'better' to do, but after you bite your lip or tongue, suffer the pain, and put on too much weight, you might realize that you DON'T.
EATING (or 'dining') should be a meditative, focussed experience. It makes it even more enjoyable, and less harmful. Be grateful that you have food to eat and time to eat it. There is plenty of time to say something BETWEEN bites (not while chewing, which is rude anyway), and if you must read or watch the tube while eating, or for some reason eat on the run, keep in mind the danger and BE CAREFUL (it's WORTH it, and that is that).