I have heard that on one occasion the Blessed One was staying near Savatthi, in Jeta's Grove, Anathapindika's monastery. There he addressed the monks: "Monks!"
"Yes, lord," the monks responded.
The Blessed One said: "Even if a monk is not skilled in the ways of the minds of others (not skilled in reading the minds of others), he should train himself: 'I will be skilled in reading my own mind.'
"And how is a monk skilled in reading his own mind? Imagine a young woman -- or man -- fond of adornment, examining the image of her own face in a bright, clean mirror or bowl of clear water: If she saw any dirt or blemish there, she would try to remove it. If she saw no dirt or blemish there, she would be pleased, her resolves fulfilled: 'how fortunate I am! How clean I am!' In the same way, a monk's self-examination is very productive in terms of skillful qualities if he conducts it in this way: 'Do I usually remain covetous or not? With thoughts of ill will or not? Overcome by sloth and drowsiness or not? Restless or not? Uncertain or gone beyond uncertainty? Angry or not? With soiled thoughts or unsoiled thoughts? With my body aroused or un-aroused? Lazy or with persistence aroused? Un-concentrated or concentrated?'
"If, on examination, a monk knows, 'I usually remain covetous, with thoughts of ill will, overcome by sloth and drowsiness, restless, uncertain, angry, with soiled thoughts, with my body aroused, lazy, or un-concentrated,' then he should put forth extra desire, effort, diligence, endeavor, undivided mindfulness, and alertness for the abandoning of those very same evil, unskillful qualities. Just as when a person whose turban or head was on fire would put forth extra desire, effort, diligence, endeavor, undivided mindfulness, and alertness to put out the fire on his turban or head; in the same way, the monk should put forth extra desire, effort, diligence, endeavor, undivided mindfulness, and alertness for the abandoning of those very same evil, unskillful qualities.
"But if, on examination, a monk knows, 'I usually remain un-covetous, without thoughts of ill will, free of sloth and drowsiness, not restless, gone beyond uncertainty, not angry, with unsoiled thoughts, with my body un-aroused, with persistence aroused, and concentrated,' then his duty is to make an effort in establishing ('tuning') those very same skillful qualities to a higher degree for the ending of the effluents."