You're not the first person whom I have heard say that. Why do you allow it to irritate you? Do you have so little confidence in your driving ability that you can't ignore them? Keep a firm speed, don't slow down or speed up, and ignore them. If you're not breaking the law you have nothing to worry about. It's the aggressive driver who is in breaking the law. There are laws in most (if not all) States about tailgating.
Lifey