Hi GreenTea,
Be careful to avoid changing the practice in order to try to produce a certain effect. In this case: Forcing a deeper level with extra focus, in order to produce a more pronounced effect on the nervous system. There are thousands of ways in which the practice of Deep Meditation could be altered in subtle ways, to produce different results. But once we start down that road, what we are doing is chasing experiences. So, we are no longer meditating. We are creating an idea in the mind, such as “a more pronounced effect on the nervous system is better”, and then adjusting the way we practice to bring the desired effect.
Deep Meditation works, because it is not about chasing experiences. So, it does not matter at all what happens. If we notice that we are off the mantra, we easily favour the mantra again. Any perceived effects on the subtle nervous system are irrelevant. This is important, because it means we are not chasing anything, and not grasping after anything. There is a relaxation in the mind that happens when there is no desire for any outcome. And this relaxation leads to inner silence, and then to vairagya, and eventually to yoga (union).
Moderator note: Some replies to this post were moved to here for better placement.