The Bhagavad Gita with Commentaries of Ramanuja, Madhva, Shankara and Others.
Bhagavad Gita 6.20-23
http://www.bhagavad-gita.us/articles/420/1/Bhagavad-Gita-620-23/Page1.html
By Bhagavan Sri Krishna
 

Text 20-23

yatroparamate cittam
niruddham yoga-sevaya
yatra caivatmanatmanam
pasyann atmani tusyati

sukham atyantikam yat tad
buddhi-grahyam atindriyam
vetti yatra na caivayam
sthitas calati tattvatah

yam labdhva caparam labham
manyate nadhikam tatah
yasmin sthito na duhkhena
gurunapi vicalyate

tam vidyad duhkha-samyoga-
viyogam yoga-samjnitam

Translation

In the stage of perfection called trance, or samadhi, one’s mind is completely restrained from material mental activities by practice of yoga. This perfection is characterized by one’s ability to see the self by the pure mind and to relish and rejoice in the self. In that joyous state, one is situated in boundless transcendental happiness, realized through transcendental senses. Established thus, one never departs from the truth, and upon gaining this he thinks there is no greater gain. Being situated in such a position, one is never shaken, even in the midst of greatest difficulty. This indeed is actual freedom from all miseries arising from material contact. 

Commentary by Srila Prabhupada 

By practice of yoga one becomes gradually detached from material concepts. This is the primary characteristic of the yoga principle. And after this, one becomes situated in trance, or samadhi, which means that the yogi realizes the Supersoul through transcendental mind and intelligence, without any of the misgivings of identifying the self with the Superself. Yoga practice is more or less based on the principles of the Patanjali system. Some unauthorized commentators try to identify the individual soul with the Supersoul, and the monists think this to be liberation, but they do not understand the real purpose of the Patanjali system of yoga. There is an acceptance of transcendental pleasure in the Patanjali system, but the monists do not accept this transcendental pleasure, out of fear of jeopardizing the theory of oneness. The duality of knowledge and knower is not accepted by the nondualist, but in this verse transcendental pleasure—realized through transcendental senses—is accepted. And this is corroborated by Patanjali Muni, the famous exponent of the yoga system. The great sage declares in his Yoga-sutras (3.34): purushartha-shunyanam gunanam pratiprasavah kaivalyam svarupa-pratishtha va citi-shaktir iti. 

This citi-shakti, or internal potency, is transcendental. Purushartha means material religiosity, economic development, sense gratification and, at the end, the attempt to become one with the Supreme. This “oneness with the Supreme” is called kaivalyam by the monist. But according to Patanjali, this kaivalyam is an internal, or transcendental, potency by which the living entity becomes aware of his constitutional position. In the words of Lord Caitanya, this state of affairs is called ceto-darpana-marjanam [Cc. Antya 20.12], or clearance of the impure mirror of the mind. This “clearance” is actually liberation, or bhava-maha-davagni-nirvapanam. The theory of nirvana—also preliminary—corresponds with this principle. In the Bhagavatam (2.10.6) this is called svarupena vyavasthitih. The Bhagavad-gita also confirms this situation in this verse. 

After nirvana, or material cessation, there is the manifestation of spiritual activities, or devotional service to the Lord, known as Krishna consciousness. In the words of the Bhagavatam, svarupena vyavasthitih: this is the “real life of the living entity.” Maya, or illusion, is the condition of spiritual life contaminated by material infection. Liberation from this material infection does not mean destruction of the original eternal position of the living entity. Patanjali also accepts this by his words kaivalyam svarupa-pratishtha va citi-shaktir iti. This citi-shakti, or transcendental pleasure, is real life. This is confirmed in the Vedanta-sutra (1.1.12) as ananda-mayo ’bhyasat. This natural transcendental pleasure is the ultimate goal of yoga and is easily achieved by execution of devotional service, or bhakti-yoga. Bhakti-yoga will be vividly described in the Seventh Chapter of Bhagavad-gita. 

In the yoga system, as described in this chapter, there are two kinds of samadhi, called samprajnata-samadhi and asamprajnata-samadhi. When one becomes situated in the transcendental position by various philosophical researches, he is said to have achieved samprajnata-samadhi. In the asamprajnata-samadhi there is no longer any connection with mundane pleasure, for one is then transcendental to all sorts of happiness derived from the senses. When the yogi is once situated in that transcendental position, he is never shaken from it. Unless the yogi is able to reach this position, he is unsuccessful. Today’s so-called yoga practice, which involves various sense pleasures, is contradictory. A yogi indulging in sex and intoxication is a mockery. Even those yogis who are attracted by the siddhis (perfections) in the process of yoga are not perfectly situated. If yogis are attracted by the by-products of yoga, then they cannot attain the stage of perfection, as is stated in this verse. Persons, therefore, indulging in the make-show practice of gymnastic feats or siddhis should know that the aim of yoga is lost in that way. 

The best practice of yoga in this age is Krishna consciousness, which is not baffling. A Krishna conscious person is so happy in his occupation that he does not aspire after any other happiness. There are many impediments, especially in this age of hypocrisy, to practicing hatha-yoga, dhyana-yoga and jnana-yoga, but there is no such problem in executing karma-yoga or bhakti-yoga. 

As long as the material body exists, one has to meet the demands of the body, namely eating, sleeping, defending and mating. But a person who is in pure bhakti-yoga, or in Krishna consciousness, does not arouse the senses while meeting the demands of the body. Rather, he accepts the bare necessities of life, making the best use of a bad bargain, and enjoys transcendental happiness in Krishna consciousness. He is callous toward incidental occurrences—such as accidents, disease, scarcity and even the death of a most dear relative—but he is always alert to execute his duties in Krishna consciousness, or bhakti-yoga. Accidents never deviate him from his duty. As stated in the Bhagavad-gita (2.14), agamapayino ’nityas tams titiksasva bharata. He endures all such incidental occurrences because he knows that they come and go and do not affect his duties. In this way he achieves the highest perfection in yoga practice.

Commentary by Sri Visvanatha Cakravarti Thakur

In verse 16 and the verses following, the word yoga referred to being situated in samadhi. Samadhi is of two types: samprajnata and asamprajnata. Samprajnata samadhi has many types according to differences of savicara and savitarka.

What is asamprajnata samadhi like? Three and a half verses answer. In that state of asamprajnata samadhi, the consciousness does not touch any objects at all (cittam uparamate), because of complete stoppage (niruddham). As Patanjali's sutra says: yogas citta-vrtti-nirodhah : yoga means stopping the functions of the consciousness. (Yoga Sutra 1.2) The word yatra (in which state) extends its meaning to verse 23.

In that samadhi, the yogi, seeing the self by his consciousness (atmana) in the form of paramatma, is satisfied in the self. In that state of samadhi, he then experiences extreme bliss, which is  comprehended  by  intelligence  in   the  form  of  the  soul (buddhya), devoid of contact with material senses and sense objects. Then, in that state he does not move from the true state of the atma, his true form (tattvatah). Having attained that state, he does not consider attaining anything else. In that state, he is separated from all contact with suffering. One should know that state of samadhi as yoga.

"Though I cannot attain it quickly, certainly I can attain this yoga." By such certainty one should practice. One should not be discouraged, saying, "After such a long time, I have not achieved perfection. What is the use of all this hard work?" (anirvinna cetasa). One should practice with mind convinced, "What is it to me? Let me attain perfection in this life or in the next."

Gaudapada has given an example:

utseka udadher yadvat kusagreaika-binduna manaso nigrahas tadvad bhaved aparikhedatah

One should gradually control the mind without complaining, though it is like taking drops of water from the ocean to dry it up with a tip of a kusa.

There is a story to explain this. The ocean stole with its strong waves the eggs of a bird which were situated on the ocean's shore. Determined to dry up the ocean, the bird took one drop of water at a time using its beak. The ocean, being emptied of many drops by the bird's beak, was not at all affected. Though discouraged by Narada, who happened to come there, the bird again made the promise in front of him. "In this life or the next, I will dry up the ocean."

Then merciful Narada, by the will of the Lord, send Garuda to help the bird, saying "The ocean has disrespected you by offending your relative, this small bird." The ocean, becoming dried up by the wind coming from Garuda's flapping wings, became frightened, and then returned the eggs to the bird.

Thus one should be convinced that the Lord will bestow his mercy on the resolute person who enthusiastically begins yoga, jnana or bhakti with faith in the words of scripture.