The cranial bones of the skull are all interconnected by longitudinal joints called sutures (think of the soft spot on a baby's head). These delicate interfaces between bones are actually designed to move slightly as one breathes. Just beneath these bones lies a network of fluid called cerebrospinal fluid, or CSF, that ensheathes the brain and provides nutrition and shock absorber support to the nervous system. Thus, the importance of breathing properly becomes quite transparent when this mechanisms is well understood. People tend to stop breathing adequately when they are under stress. Since the world in which we live today is littered with stressors, most individuals are not breathing properly throughout the day, which is difficult to notice because we rarely even think of our breathing since it is such a subconscious process.
When our breathing becomes shallow due to stress throughout the day, the cranial bones begin to 'breathe' less and less and tensions are created along the cranial joint or suture lines. This is similar to a fault line on the Earth that creates an earthquake when there is enough tension in it. As these bones begin to move less and less, the underlying CSF begins to become hampered as well, interfering with proper brain nourishment, function and support. Many headaches are the result of cranial tension from lack of breathing as well. This whole nasty chain of events started with lack of proper breathing.
Throughout your day, stop yourself and ask, 'Do I feel I am breathing in the best way that I can for my body?' Focus on bringing your breath deep down into your diaphragm and making your breaths a bit longer if you find you are breathing little. Each person is different, and thus the best judge of what breathing is best for you is you.