This is also related closely to a practice in the Buddhist and Hindu traditions called Anapanna. It is simply a practice of learning how to be mindful of the breath, all the time, to be watching the breath. We obviously need to breath to remain alive, but we do it mechanically. Most of the time we are not even aware of the process of breathing, and so we just go about our business not fully aware and cognizant that the breath is what keeps us alive. So by becoming conscious of that, and learning to maintain an awareness of the process of breathing, we start to become more conscious of ourselves and to work with the force of the consciousness.
In relation to the breath, this is very important, because when you are breathing you are drawing in Prana. Remember that all the air that is drawn in is then absorbed into the blood, which is cycled throughout the body to feed your organism, your physical body, and sustain it. So when you start to breathe consciously, you breathe in better and more pure elements. You start to bring in the influence of the consciousness, and the consciousness is a direct extension of God. So learning to be conscious of breath can begin a very incipient level of self-awareness.