The Gratitude Rock works on the principles of "The Law of Attraction" which states that like energy attracts like energy, like a magnet. Energy of a certain quality or vibration tends to attract energy of a similar quality and vibration. You attract to you the essence of whatever you are predominantly thinking about. If you are consistently thinking about what you already have and express your gratefulness for having it, your results will reflect more of that. (By the same token, if you are consistently thinking about what you do not have, your results will equally reflect that.)
Whatever you hold your attention on, you will attract, IF you know how to do it and how to apply it in your life with exact precision and how to use it with 100% accuracy. When used properly, it is absolutely infallible, as predictable as gravity, because it is a Universal Law that cannot be changed.