Eating sandwiches on the go or stuffing down a fast food meal while driving is something that shouldn't even be a habit in the first place. Driving while eating is dangerous, and when you eat while heading one from one place to another, you're not registering what and how much you're eating. Maybe you could have saved half of that 12-inch sub for later, or you still feel hungry afterward because you ate so fast. Whatever the case, try to make a concerted effort to eat all your meals sitting down, without distractions.