Japa Sadhana or Mantra Chanting is important to the Sadhaks because to make what is explained in texts has to be realized with your physical body ( Sthula Sharira) itself. The energetic link between the lower and higher bodies is the breath or Prana and the path to transcendence lies in its neutralization. Every technique of Upasana is in one way or the other aimed at modifying the breath current or Prana so as to refine it and intensify awareness of the subtle and inner breath currents connected with the higher bodies. The simplest way to accomplish the same is through the might of unmoving attention directed towards an external or internal object, breath itself being an important option. The acts of silencing the mind and the breath are interconnected and mantra is an important way to accomplish both.
Through the chanting of the Mantra your body becomes Mantra Sarira. You are elevated to the status of a Divyatma –a blessed soul. The Sadhak will start losing evil habits and get into cosmic body which makes him to lead a materially and spiritually vibrant life.
The generally chaotic mind has its own pattern of radiation and energetic imagery, and that keeps changing infinitely. Similarly, mantra, which has an energetic mind of its own, also has a specific energetic pattern associated with it. This pattern is generally traceable to a deity or a seer associated with the mantra. As the mantra is repeated over and over in the mind, more importantly with utmost mindfulness, the ripples of energy produced in the mind by the mantra slowly begin to transform the energetic make of the subtle bodies, molding them to resemble the energetic make of the mantra, and eventually of the deity ( Siva) represented by the mantra ( Om Nama Sivayah). It is my experience and assurance that Sadhak may get cured all diseases connected with body and mind if any thing is prevailing. If Lord permits one can see his own Atman ( Soul) by chanting this mantra.