Your body can live without food for perhaps weeks; without water for a day or two; but without air, the body will be a cadaver in just a few minutes.
Breath is necessary for life, but there is more to it than most people know. Swami Rama said that "Breath is a barometer to measure one's inner state." (Sadhana, The Essence of Spiritual Life, Pp. 89).
We can watch this barometer by being aware of whether the breath is deep or shallow, smooth or jerky, and diaphragmatic or thoracic.
A shallow, jerky, thoracic breath is associated with a feeling of agitation inside, while a deep, smooth, diaphragmatic breath is associated with inner calm.
The science of breath is one which every person can practice and learn. We all breathe.
So next time you notice that you're feeling agitated, anxious, or emotional, take note of your breathing and seek to make the breath deep, smooth and diaphragmatic. In a short period of time, you'll likely feel calmer and your mind will become clearer and more able to assess whatever situation you're in.