I always have to travel with some food. A sleeve of cookies or a box of crackers or at least an apple or something. I hate to be hungry and I get hungry a lot. If I am on a long car or bus or train trip and there is nothing to eat I start to get really cranky. I know that I am not a very pleasant person to be around when I am like that.
For that reason I always make sure that I have something to snack on just in case there is no where else to buy food. It is kind of like being a smoker. If you think you are about to run out of cigarettes you will grab a fresh pack before you leave the house. I do this with saltines.