Be completely empty.
Be perfectly serene.
The ten thousand things arise together;
in their arising is their return.
Now they flower,
and flowering
sink homeward,
returning to the root.
The return to the root
is peace.
Peace: to accept what must be,
to know what endures.
In that knowledge is wisdom.
Breathing is one internal function that the conscious mind can control with comparative ease. The effect of controlled breathing is almost like communication with all conscious parts of one's being saying to them, "Simmer down and listen; there is something beyond the turmoil". It is communication in action that often works when words merely go in one ear and out the other, not even changing the cognitive mind. In essence, the effect is to turn all the elements of our will toward stillness and waiting.