When the attempt at control is stopped, awareness arises that thinking itself has stopped. This stillness then continues by itself, effortlessly. If through inexperience, lack of instruction, unfamiliarity, or unpreparedness fear is felt, fear of death, annihilation of consciousness, this extremely subtle and delicate experience will suddenly come to an end. The opportunity is lost.
-- Notebooks Category 23: Advanced Contemplation > Chapter 7: Contemplative Stillness > # 312