The succeeding lines of Yoga Sutras (namely, all remaining lines of the section) are dedicated to cognition. So I shall lay down a few considerations to make the reader mentally prepared.
Most of Western people erroneously take yoga as a system of physical exercises. A kind of gymnastics. However, hatha-yoga is just a small element of this multifacetous tradition. Physical practices definitely played an important – yet auxiliary - role. They trained the body to keep it healthy and live long; the body that was used as a key to one’s inner world. But authentic yoga practice implies inner transformation that was based on merger with one’s genuine, innermost essence – svarupa – by means of taking under control factors that were separating one from it. This basic nature of yoga is emphasized in the etymology of the word yuj that denotes both “joining together” (samadhi) and “taking control of” (samyama) – see here for details.
The concept that a man is actually estranged from oneself may at first sight appear to be spacy, yet when learning more about modern neurophysiology findings we shall see this to be a healthy judgement. For instance, they have proved that human brain takes decision several minutes before one has consciously made it. And this refers to some simple issues … We spend years in the agony of “choosing”, but deep inside the decision has been made long time ago…