Yoga is mastery over the mind, where one stays in his/her own true nature.
How to get this mastery over the mind?
The next 4 Sutra is talking about 2 means for a extraordinary qualified student.
Abhyasavairagyabhyam tannirodhah । 1-12 That mastery over the mind is gained through repetition of practice and dispassion. Tara sthitau yatnobhyasah । 1-13
Abhyasa is the effort to secure steadiness.
In another word, “practice makes perfect”.
Sa tu dirghakalanairantaryasatkarasevito drdhabhumih । 1-14 And this practice become firmly grounded when practice in a long time, without any break and with perfect devotion.
Drstanusravikavisayavitrsnasya vasikarasanjna vairagyam । 1-15
Vairagyam is Non attachment toward the object of enjoyment seen here and heard from scripture (heaven etc), in which one aware that he is having control of those object.
4 types variragyam are presented here:
Yatamāna, struggling / attempt not let the mind run to the object.
Vyatireka, ruthlessly avoid them.
Aikendryam indriya, senses are stand still, only mind has like or dislike of the object. Mind and senses are function independently.
Vasikaram, this is highest state of vairagya. Mind also free form like and dislike.
Only by viveka (discriminative knowledge) then vairagya come.
Why? Because only know how to discriminate what is good for me and what is not, one can decide to stay away from the object first, and slowly outgrown it.
Same way in the meditation, we need to know what activities is not good for us, like avoid talking just before meditation or not to meditate with full stomach. And slowly the viveka upgraded to Ātma and anātma viveka, by knowing my true nature from sastra study, then it will culminate in to vairagya towards what is not my true nature.
Isvarapranidhanadva । 1-23
Or devotion and surrender to the God.
What is devotion? When we say that someone is a devotee because we can see the person doing a lot of act of worship. How about at the time he is not doing puja, can he still called as devotee?
In Bhagavad-Gita chapter 7-16, four types of devotee is described:
Ārtah is one who is seized by a distress.
arthārthi invokes the grace of īsvara asking for desires.
Jijñāsu is the one who desires to know Īsvara.
Jnāni is one who recognise the oneness with Isvara.
Among this 4, Jnani is the dearest devotee, because the culmination of devotion is to see one's true nature is not different from Isvara.
How about surrender? This word can give connotation that one just accepts everything without doing anything. In another word surrender to Isvara means having the Karma yoga attitude. Karma yoga is not "doing something for others without any expectation".
Karma yoga attitude is offering the action to īsvara (doing what is to be done as my duty and in any giving situation, by seeing it as the order of Isvara) this is devotion. And accept the result of our actions as prasadam (lord’s grace), this is called surrender.