Search out the point where your thoughts arise and disappear. See where a thought rises and where it vanishes.Keep this point in mind and try to break right through it; try to crush it with all your might! If you can crush it to pieces, all will dissolve and vanish away. At this time, however, one must not follow it [the instantaneous experience] nor try to continue it. Master Yung Chia once admonished, "The thought of continuation should be cut short." This is because floating, delusory thoughts are virtually rootless and unreal. Never treat the distracted thought as a concrete thing. When it arises, notice it right away but never try to suppress it. Let it go and watch it as one watches a calabash floating on the surface of a stream.
What you should do is take up this awareness as if holding a sharp sword in your hand. No matter whether Buddha or devils come, just cut them off like a snarl of entangled silk threads. Use all your attention and strength patiently to push your mind to the very dead end [of consciousness]; just push it on and on.
Those who determine to practice the Dharma should believe firmly the teaching of Mind-only. Buddha said, "All the Three Kingdoms are mind, all ten thousand Dharmas are consciousness." All Buddhism is nothing but an exposition of this sentence. Ignorance or Enlightenment, virtue or wickedness, cause or effect, are nothing but one's own mind. Not one iota of anything exists outside of Mind. The Zen yogi should completely cast aside his former knowledge and understandings. Here scholarship or cleverness is useless. Rather, he should look on the whole world as hallucinatory. What he sees are mirages, mirror-images, like the moon reflected in the water. The sounds he hears are hymns of the wind blowing through the trees. He should see all manifestations as clouds floating in the sky-changing and unreal. Not only the outer world, but all habitual thoughts, passions, distractions, and desires within one's own mind are, likewise, insubstantial, non-concrete, rootless, and floating.
-Chang Chen-Chi, The Practice of Zen