bandhur ātmātmanas tasya
yenātmaivātmanā jitaḥ
anātmanas tu śatrutve
vartetātmaiva śatru-vat

Translation of Bhagavad Gita 6.6

For him who has conquered the mind, the mind is the best of friends; but for one who has failed to do so, his mind will remain the greatest enemy.

Commentary by Sri A.C. Bhaktivedanta Swami Prabhupada of Gaudiya Sampradaya:

The purpose of practicing eightfold yoga is to control the mind in order to make it a friend in discharging the human mission. Unless the mind is controlled, the practice of yoga (for show) is simply a waste of time. One who cannot control his mind lives always with the greatest enemy, and thus his life and its mission are spoiled. The constitutional position of the living entity is to carry out the order of the superior. As long as one’s mind remains an unconquered enemy, one has to serve the dictations of lust, anger, avarice, illusion, etc. But when the mind is conquered, one voluntarily agrees to abide by the dictation of the Personality of Godhead, who is situated within the heart of everyone as Paramatma. Real yoga practice entails meeting the Paramatma within the heart and then following His dictation. For one who takes to Krishna consciousness directly, perfect surrender to the dictation of the Lord follows automatically.

Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

The mind is whose friend and whose enemy? This verse answers. The mind (atma) is a friend, causing benefit, to that jiva who has conquered the mind. The mind acts as an enemy, causing harm, to that jiva who does not control the mind (anatmanah).

Commentary by Sri Ramanuja of Sri Sampradaya:

6.6 A person whose mind is conquered by himself in relation to sense-objects, has that mind as his friend. In the case of one whose mind is not conquered in this way, his own mind, like an enemy, remains hostile. The meaning is that it acts, against his attainment of supreme beatitude. It has been stated by Bhagavan Parasara also: ‘The mind of man is the cause both of his bondage and his release. Its addiction to sense objects is the cause of his bondage; its separation from sense objects is the means of one’s release’ (V. P., 6.7.28). The proper condition for the beginning of Yoga is now taught:

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

Evidence of the minds friendliness is elucidated now by Lord Krishna. Freedom from all dualities such as heat and cold, praise and ridicule, joy and grief. Continuously poised and serene within meditating on the atma or soul. Another interpretation is that the awakened individual soul has attained communion with the ultimate soul establishing it in his heart.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

Sri Madhvacharya did not comment on this sloka.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

After previously describing that a person who has conquered their mind is there own best friend and after explaining the special qualities possessed by one who has climbed the heights and is detached from sense impulses. Lord Krishna now refers to the person who has traversed successfully the path of yoga or the science of the individual consciousness attaining communion with the ultimate consciousness and has become firmly established in their spiritual nature. Such a person has transcended all dualities such as cold and heat, happiness and distress, honour and dishonour. Such persons are serene and peaceful in all situations because they are established in spiritual knowledge from the Vedic scriptures.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

6.6 Tasya, of him; yena, by whom; jitah, has been conquered, subdued; his eva atma, very self, the aggregate of body and organs; that atma, self; is bandhuh, the friend; atmanah, of his self. The idea is that he is a conqueror of his senses. Tu, but; anatmanah, for one who has not conquered his self, who has no self-control; atma eva, his self itself; varteta, acts; satruvat, like an enemy; satrutve, inimically, with the attitude of an enemy. As an enemy, who is different from oneself, does harm to oneself, similarly one’s self behaves like an enemy to oneself. This is the meaning. [If the body and organs are under control, they are helpful in concentrating one’s mind on the Self; but, if they are not under control, they oppose this concentration.]

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

6.5-6 Uddharet etc. Bandhuh etc. In this [path] there is no other means excepting the self i.e. nothing but one’s mind. Indeed the subdued mind is a friend and it lifts up [the Self] from the highly dreadful cycle of birth and death. But the unsubdued one does the act of enmity as it throws [the Self] down in the horrible hell. The characteristic mark of the subdued-minded man is this :

Sanskrit Shloka Without Transliteration Marks:

bandhur atmatmanas tasya
yenatmaivatmana jitah
anatmanas tu satrutve
vartetatmaiva satru-vat

Sanskrit to English Word for Word Meanings:

bandhuḥ — friend; ātmā — the mind; ātmanaḥ — of the living entity; tasya — of him; yena — by whom; ātmā — the mind; eva — certainly; ātmanā — by the living entity; jitaḥ — conquered; anātmanaḥ — of one who has failed to control the mind; tu — but; śatrutve — because of enmity; varteta — remains; ātmā eva — the very mind; śatru-vat — as an enemy.