Practice (abhyasa) means choosing, applying the effort, and doing those actions that bring a stable and tranquil state (sthitau).
When the mind loses desire even for objects seen or described in a tradition or in scriptures, it acquires a state of utter (vashikara) desirelessness that is called non-attachment (vairagya).
Those who pursue their practices with intensity of feeling, vigor, and firm conviction achieve concentration and the fruits thereof more quickly, compared to those of medium or lesser intensity.
1.30 Nine kinds of distractions come that are obstacles naturally encountered on the path, and are physical illness, tendency of the mind to not work efficiently, doubt or indecision, lack of attention to pursuing the means of samadhi, laziness in mind and body, failure to regulate the desire for worldly objects, incorrect assumptions or thinking, failing to attain stages of the practice, and instability in maintaining a level of practice once attained.
1.31 From these obstacles, there are four other consequences that also arise, and these are: 1) mental or physical pain, 2) sadness or dejection, 3) restlessness, shakiness, or anxiety, and 4) irregularities in the exhalation and inhalation of breath.
1.32 To prevent or deal with these nine obstacles and their four consequences, the recommendation is to make the mind one-pointed, training it how to focus on a single principle or object.
1.34 The mind is also calmed by regulating the breath, particularly attending to exhalation and the natural stilling of breath that comes from such practice.
1.39 Or by contemplating or concentrating on whatever object or principle one may like, or towards which one has a predisposition, the mind becomes stable and tranquil.
1.48 The experiential knowledge that is gained in that state is one of essential wisdom and is filled with truth.
1.49 That knowledge is different from the knowledge that is commingled with testimony or through inference, because it relates directly to the specifics of the object, rather than to those words or other concepts.
2.1 Yoga in the form of action (kriya yoga) has three parts: 1) training and purifying the senses (tapas), 2) self-study in the context of teachings (svadhyaya), and 3) devotion and letting go into the creative source from which we emerged (ishvara pranidhana).
2.5 Ignorance (avidya) is of four types: 1) regarding that which is transient as eternal, 2) mistaking the impure for pure, 3) thinking that which brings misery to bring happiness, and 4) taking that which is not-self to be self.
2.15 A wise, discriminating person sees all worldly experiences as painful, because of reasoning that all these experiences lead to more consequences, anxiety, and deep habits (samskaras), as well as acting in opposition to the natural qualities.
2.29 The eight rungs, limbs, or steps of Yoga are the codes of self-regulation or restraint (yamas), observances or practices of self-training (niyamas), postures (asana), expansion of breath and prana (pranayama), withdrawal of the senses (pratyahara), concentration (dharana), meditation (dhyana), and perfected concentration (samadhi).
Credit to http://www.swamij.com/yoga-sutras-list.htm.