Most of us, most of the time leave breathing to our autonomic nervous systems as an automatic function. I have come to realize that breathing is one of the most miraculous of treasures that we all have that is right in front of us all the time!
By making breathing a conscious activity, the health benefits (as well as general life benefits) are immense. First of all, just considering the breath as a miracle as you observe it is in and of itself a wonderfully uplifting practice. All the millions of intricate chemical processes that happen with each breath in and out is truly astounding, especially when you consider that ALL body processes depend on the breath to continue. That sounds obvious, but in the context of the miracle of life it bears pointing out.
Conscious breathing means that you couple the imagination with the breath, and in that way create a powerful mind-body connection.
Consider this: When breathing unconsciously, when you breath in, you are merely breathing in air, and when you breath out, you're just exhaling the metabolic wastes into the atmosphere. With conscious breathing, however, you use the mind via the imagination to supercharge that air you breath in with the subtle energies you create.
Breathe in LOVE, breathe in LIGHT, breathe in ABUNDANCE, breathe in HEALTH, breathe in whatever you want to see happen in your life. Then, do the same on the out breath, but send it out into the world--to your friends, your family, the entire planet. In this way you complete the circle of life and build karmic momentum. Feel the planet breathing you, feel you breathing the planet.
By working consciously with the breath, you make your life more conscious, and you improve the world!