Answers to Questions on the Contemplative Practice (vipaśyanā-caryā) of the Four Foundations of Mindfulness 25

Question: Last night starting at 11:30 I sat in meditation on the sofa in half-lotus posture. After reciting the Heart Sutra my mind calmed down, and I began observing the breath, gradually entering a state between sleeping and waking. After about 30 minutes my body felt comfortable and light, floating. Then slowly my body began to vibrate, and the vibration grew larger and larger... I couldn't control myself anymore; there was no breath, my body was swaying, my eyes wouldn't open, my heartbeat quickened and I felt I was about to breathe my last... I knew it in my mind but couldn't control myself... I was very frightened, feeling that I was about to die. I couldn't cry out, couldn't shout, couldn't move, and only with great difficulty did I fall over. It took a long time before I regained my calm. 

Answer: When first cultivating meditative concentration (samādhi), after the mind becomes still and the qi channels run well, there may be the phenomenon of qi-mechanism activation. This is a good sign of opening up the body's channels and can regulate the body very well. If your physical condition is very poor, do not enter samādhi all at once; take it slowly, regulating the body bit by bit, so as to avoid a sudden onset that you cannot adapt to. 

At the beginning, entering and leaving samādhi happens involuntarily; the body is controlled by the qi-mechanism and does not quite obey your own direction. After a long time this will ease considerably, and you will be able to control it and have the final say. When the body's qi-mechanism activates, just relax and let go—pay no attention to anything. The emptier the mind, the better; the more untroubled, the better. Just keep emptying yourself. Be willing to be empty, dare to be empty—once empty, there is nothing to worry about.