The three elements referred to are your body, your speech (which includes your emotions) and your mind. The idea is that when you practice sincerely and deeply, it will show in your body, the way you speak and deal with your emotions, and the way that your mind works.
Your practice will show in your body by the way that you move and the way that you relate to physical space and objects. This doesn’t mean that your body will be physically ‘perfect’ by some outer standard. It means that you will move with more balance, more strength, more grace. Simply put, you become comfortable in your own skin and you learn how to work with its particular challenges.
Your practice will show in your speech and emotions in that you will develop the ability to speak and act more skillfully. This means that you will learn not to allow your expression to be driven by habit, but will apply your training to developing the ability to express yourself in the moment.
Your practice will show in your mind by the awareness you have of how it works. When you spend time observing your mind in action as a detached observer, you learn about your habits and patterns and you learn to allow your mind to relax and expand.
The slogan tells us that lojong, while it is concerned directly with the mind, is applicable to our bodies and our speech as well. The three form a trinity that cannot be separated.