Niyama
नियम (niyama)
Observance - the second limb of classical yoga, the disciplines addressed toward oneself.
Where yama governs conduct toward others, niyama governs conduct toward oneself: purity, contentment, disciplined effort, self-study, and surrender to what is beyond one's control.
Together, yama and niyama form a complete ethical foundation before the physical and meditative limbs begin, addressing both the outward relationship to others and the inward relationship to oneself. Neither is considered sufficient alone.
Contentment (santosha) among the niyamas is worth particular attention: it is listed as a discipline, not a mood, suggesting that contentment is something practiced and cultivated rather than simply felt when circumstances happen to be favorable.