If our ordinary, self-centered viewpoint is dominant, rocks and tree roots are undesirable. But if we change our point of view, then the very fact that there are rocks and tree roots makes the valley stream more beautiful and the sight of waves breaking upon them beyond description. When we perceive joy, anger, happiness and sorrow as enriching our lives, just as rocks and tree roots and water spray embellish nature, then we are able to accept whatever happens and live like flowing water, without clinging to anything.
The discipline of silence doesn't mean just taking a short vacation from the spoken word. It also means giving complete relaxation to the muscles, the tissues, the tongue itself. A modern writer once said: "Knowledge has never been known to enter the head via an open mouth." It is when you become completely silent that you are able to absorb knowledge. God speaks in silence. The discipline of silence is essential on the path.