At off intervals during the day, he is to pull himself up abruptly and note the nature and character of his thoughts. Then he is to ask himself why he is holding them or what is impelling him towards them. The purificatory worth of this practice is great. It gives him the chance to become aware of negatives and throw them out, but best of all it trains him in detachment. From this exercise he is to go on to its sequel, which applies the same attitude towards what the body's senses tell him and also towards what his emotions and passions make him feel.
-- Notebooks Category 2: Overview of Practicies Involved > Chapter 6: Self-Reflection and Action > # 5