B.G 6.05 and 06

उद्धरेदात्मनाऽत्मानं नात्मानमवसादयेत्। आत्मैव ह्यात्मनो बन्धुरात्मैव रिपुरात्मनः ॥५॥

One should uplift himself with the help of mind and should not degrade. Certainly, the mind alone is the friend of oneself, and also the enemy.

बन्धुरात्माऽत्मनस्तस्य येनात्मैवाऽत्मना जितः। अनात्मनस्तु शत्रुत्वे वर्तेताऽत्मैव शत्रुवत् ॥६॥

The mind becomes the friend of oneself, by whom indeed the mind is conquered with the help of the lord. But the unconquered mind turns hostile. Indeed, such a mind acts like an enemy.

Gīta Bhāshya 6.05 and 06

Striving is necessary to ascend to the summit of Yoga. 'ātmā' - mind; 'ātmanaḥ' - of the living being; 'ātmanā' - with the mind; 'ātmānaṁ' - the individual being; 'ātmaiva' - the mind; 'anātmanaḥ' - the unconquered mind of the individual.

स च योगारोहः प्रयत्नेन कर्तव्यः इत्याह - उद्धरेदित्यादिना।

The practitioner can ascent to the summit of Yoga only through striving, is stated by 'uddharet' verse.

कस्य बन्धुः आत्मा इत्यत आह - बन्धुरात्मेति।

Whose friend is the self? Now, the friend says, "The self is the friend."

आत्मा मनः। आत्मनः जीवस्य। आत्मना मनसा। आत्मानं जीवम्। आत्मैव मनः। आत्मना बुद्ध्या, जीवेनैव वा। स हि बुद्ध्या विजयति। उक्तं च -

The word 'ātmā' refers to 'mind'; the word 'ātmanaḥ' refers to 'of the living being'; the word 'ātmanā' refers to 'with the mind'; the word 'ātmānaṁ' refers to 'the individual being'; the word 'ātmaiva' refers to 'the mind'; So, indeed, the living being conquers the mind, by stationing the mind in the intellect. It is also said:

"मनः परं कारणमामनन्ति।"

"The wise declare that the mind is the supreme cause."

"मन एव मनुष्याणां कारणं बन्धमोक्षयोः।"

"The mind alone causes bondage and liberation for humans."

"उद्धरेन्मनसा जीवं न जीवम् अवसादयेत्। जीवस्य बन्धुः शत्रुश्च मन एव न संशयः॥"

"One should uplift the living being by the mind, not degrade it. The mind is both the friend and the enemy of the living being; there is no doubt."

"जीवेन बुद्ध्या हि यदा मनो जितं तदा बन्धुः शत्रुरन्यत्र चास्य। ततो जयेद्बुद्धिबलो नरस्तद्देवे च भक्त्या मधुकैटभारौ॥"

"When the mind is conquered by the intellect of the living being, then the mind becomes a friend, elsewhere it becomes an enemy. Therefore, a person conquers with the strength of intellect, and then, with devotion towards the divine, thus he overcomes the demons Madhu and Kaiṭabha."

इत्यादि ब्रह्मवैवर्ते।

- stated thus in Brahmavaivarta Purana.

अनात्मनः अजितात्मनः पुरुषस्य, अजितमनस्कस्य। सदपि मनः अनुपकारि इत्यनात्मा। सन्नपि भृत्यो न यस्य भृत्यपदे वर्तते स हि अभृत्यः। तस्य आत्मा मन एव शत्रुवत् शत्रुत्वे वर्तते ॥६॥

The word 'anātmanaḥ' refers to the unconquered mind of the individual, i.e. to one whose mind is unconquered. If the mind is not helpful, it is the same as non-existent. If a servant exists, but does not conduct himself as a servant, then he is as good as non-existent for a master, and the master becomes a non-master. Similarly, the mind becomes an enemy for one whose mind behaves like an enemy (and thus, he is termed as 'anātmanaḥ').