The meaning of discipline in yoga is self-mastery. The Sanskrit term used by Patanjali expresses the goal: “Tapas” is “that which generates heat or energy.” Discipline in yoga philosophy as explained by Patanjali is the practice of directing or channeling energies towards a spiritual goal and thereby realizing greater light or energy. Discipline is not grim or negative, it is joyous and positive because it generates greater light and energy.
Tapas, according to Patanjali, is continuous and progressive practice of the balanced behaviors of yama and niyama. Yama is abstention in thought, word and deed from harming others, from falsehood, theft, incontinence and greed. It has an immediate constructive effect. All creatures feel better in the presence of one whose conduct is honest and peaceful. Thereby, greater peace and harmony are attracted to one who practices yama.
Niyama is the balancing discipline to yama, consisting of the cultivation of purity, contentment, study and devotion to God. Together, yama and niyama establish moral character until conflicting or distracting tendencies resolve harmoniously into a powerful character.
From “Frontiers of the Spirit” by Swami Kamalananda