Let us see how is MIND described by Shri Krishna.

uddhared ātmanātmānaṁ

nātmānam avasādayet

ātmaiva hy ātmano bandhur

ātmaiva ripur ātmanaḥ

This verse explains that we must use our mind to elevate ourselves rather than to degrade ourselves. Our mind is the focal point of our body. It is the part through which all the senses are controlled. It depends on us whether to use our mind for sense gratifications or for breaking all material bonds to achieve liberation.

Its aptly said in this verse that mind is the friend as well as the enemy of the conditioned soul.

The next verse continues the explanations of the above verse:

bandhur ātmātmanas tasya

yenātmaivātmanā jitaḥ

anātmanas tu śatrutve

vartetātmaiva śatru-vat

This verse continues the idea of the above verse. It explains that the mind is the best friend of those who have conquered it and it is the worst enemy for those who have failed to do so.

If a man is not able to conquer his mind then he will be attracted to various material dualities and distractions such as lust, anger and greed but those who have conquered their mind and are no longer attached to these distractions, then their mind becomes their best friend and leads them to liberation.

Let us look at another verse which extends the idea forward:

jitātmanaḥ praśāntasya

paramātmā samāhitaḥ

śītoṣṇa-sukha-duḥkheṣu

tathā mānāpamānayoḥ

In this verse Shri Krishna tells that the person who has successfully conquered his mind has already achieved the supersoul and has achieved supreme peace. For such a person is no longer under the influence of various dualities and has achieved tranquility therefore happiness and distress, heat and cold, honour and dishonour are all one and the same for him.

One more verse explains it further:

jñāna-vijñāna-tṛptātmā

kūṭa-stho vijitendriyaḥ

yukta ity ucyate yogī

sama-loṣṭrāśma-kāñcanaḥ

In this verse the great lord explains that a person is said to be true yogi only when he is fully satisfied by his acquired knowledge and his mind is under control. For him, pebbles, stones and gold are all one and the same.

The next verse goes on as follows:

suhṛn-mitrāry-udāsīna–

madhyastha-dveṣya-bandhuṣu

sādhuṣv api ca pāpeṣu

sama-buddhir viśiṣyate

According to this verse a person is said to be further advanced when he regards his friends, enemies, the pious and the sinner all with the same mind.

Lets see what the next verse tells us about:

yogī yuñjīta satatam

ātmānaṁ rahasi sthitaḥ

ekākī yata-cittātmā

nirāśīr aparigrahaḥ

This verse explains that a true transcendentalist must stay in a secluded place and must always concentrate on the lord. He should control his mind and must not hamper his realisation process due to any material desires or due to the feelings of possessiveness.

The Bhagwad geeta also tells us the ways to control the mind. The following verses will throw light on this.

śucau deśe pratiṣṭhāpya

sthiram āsanam ātmanaḥ

nāty-ucchritaṁ nāti-nīcaṁ

cailājina-kuśottaram

tatraikāgraṁ manaḥ kṛtvā

yata-cittendriya-kriyaḥ

upaviśyāsane yuñjyād

yogam ātma-viśuddhaye

Here Lord Krishna explains how to focus one’s mind onto him. He tells that one should lay grass on the ground and then should cover it with a deerskin and a soft cloth. The seat should neither be too high nor too low. The yogi must then sit on it for practicing yoga and should control his mind and the senses and must fix his mind on a fixed point.

The next verse extends the idea further:

samaṁ kāya-śiro-grīvaṁ

dhārayann acalaṁ sthiraḥ

samprekṣya nāsikāgraṁ svaṁ

diśaś cānavalokayan

praśāntātmā vigata-bhīr

brahmacāri-vrate sthitaḥ

manaḥ saṁyamya mac-citto

yukta āsīta mat-paraḥ

This verse explains that the body, head and neck should be erect in a straight line and one must stare steadily on the tip of one’s nose. With the mind devoid of every duality such as happiness and sorrow, fear and anger, heat and cold, with a vow for celibacy and free from every material desire, one must meditate upon him seeking him as the ultimate goal of his life.

The concluding verse is as follows:

yuñjann evaṁ sadātmānaṁ

yogī niyata-mānasaḥ

śāntiṁ nirvāṇa-paramāṁ

mat-saṁsthām adhigacchati

This verse explains that by exercising control over one’s mind, body and various activities, one comes out from the clutches of the material desires and finally attains to the abode of the GOD.