Sutra 1:12. Their suppression [is brought about] by persistent practice [abhyasa] and non-attachment [vairagya]. Two things are needed for the ending of mental modifications. One is abhyasa–sustained spiritual practice. This is why Krishna speaks of abhyasa yoga. The other is purely psychological: vairagya. A Brief Sanskrit Glossary defines vairagya as: “Non-attachment; detachment; dispassion; absence of desire; disinterest; or indifference. Indifference towards and disgust for all worldly things and enjoyments.”
Sutra 1:13. Abhyasa is the effort for being firmly established in that state [of chitta-vritti-nirodha].
Jnaneshwara expands on this, saying: “Abhyasa means choosing, applying the effort, and doing those actions that bring a stable and tranquil state.” Shankara simply says that abhyasa consists of the observance of yama and niyama, which are to be discussed later on.
Sutra 1:14. It [abhyasa] becomes firmly grounded on being continued for a long time, without interruption and with reverent devotion.
Vyasa: “Carried through with austerity, with brahmacharya, with knowledge and with faith, in reverence it becomes firmly grounded.”Read more »