Lord Krishna teaches Arjuna about the importance of self-discipline and the practice of meditation for achieving spiritual growth and inner peace. He describes the qualities of a true yogi, who controls their mind and senses, remains detached from worldly desires, and finds contentment within. Krishna explains the process of meditation as a way to focus the mind, suggesting a steady posture, a calm setting, and concentration on the self. He emphasizes that through dedicated practice, one can achieve self-realization, reach a state of union with the divine, and experience inner tranquility, regardless of external circumstances.