Your breathing should flow gracefully, like a river, like a watersnake crossing the water, and not like a chain of rugged mountains or the gallop of a horse. To master our breath is to be in control of our bodies and minds. Each time we find ourselves dispersed and find it difficult to gain control of ourselves by different means, the method of watching the breath should always be used.
Collected Wheel Publications Volume XVI: Numbers 231–247 (ed. Buddhist Publication Society, 2012) - ISBN: 9789552403682