Though we usually inhale and exhale unconsciously, breathing is the only vital physiological process that can also be consciously controlled. How we breathe affects our bodies and our emotions, and vice versa. In yoga, we learn to watch, explore, and move with the breath, and through it we come to find we can connect our minds and bodies and heal our emotional patterns.
We subconsciously take a greater inhalation, or inspiration, when we are in love or filled with joy, peace, and wonder. When we're happy, we often open the front of our bodies, making it easier to inhale.
Expiration, on the other hand, a word also used to describe staleness and death, leaves an emptiness readying us for our next inspiration. When we're anxious, angry, or sad, we often breathe more shallowly, shorten our inhalation, or even hold our breath. We tend to slump or clench in a way that makes inspiring more difficult.