We have a body and a mind. The mind is empty that processes various thoughts. Holy Spirit is the life energy that passes through the mind to the body. And in this process, meditation helps. Through meditation we observe every single thing in our life. Holy Spirit has two ways of moving. It can either manifest the physical reality or inwardly it can make you realize the absolute truth of life. And the whole directing thing happens with your mind.
Meditation helps to direct the Holy Spirit inward. And when the meditation includes mantras, it becomes the most powerful tool to direct the Holy Spirit. It is called Holy Spirit because the spirit that lives within you is the purest form. With it, you can direct your life and mind. The Holy Spirit rearranges itself according to your feelings, desires, thoughts, actions and emotions. Mind is the thing that works. Your emotions come from it and the Holy Spirit also works according to its direction. But when you make you of your holy spirit, it becomes the main directing tool.
Mantras contain very powerful energy that helps the Holy Spirit move inward. To make the best of your life, you must direct the Holy Spirit inwardly. And that is why mantras help in the best possible way.