The nature of the mind is flickering and unsteady. But a self-realized yogī has to control the mind; the mind should not control him. One who controls the mind (and therefore the senses as well) is called gosvāmī, or svāmī, and one who is controlled by the mind is called go-dāsa, or the servant of the senses. A gosvāmī knows the standard of sense happiness. In transcendental sense happiness, the senses are engaged in the service of Hṛṣīkeśa, or the supreme owner of the senses—Kṛṣṇa. Serving Kṛṣṇa with purified senses is called Kṛṣṇa consciousness. That is the way of bringing the senses under full control. What is more, that is the highest perfection of yoga practice.
(Bhagavad-Gita---6:26---purport).

The activities of the living entity in the body of a dog may be experienced in the mind of a different body; therefore those activities appear never to have been heard or seen. The mind continues, although the body changes. Even in this life-span we can sometimes experience dreams of our childhood. Although such incidents now appear strange, it is to be understood that they are recorded in the mind. Because of this, they become visible in dreams. The transmigration of the soul is caused by the subtle body, which is the storehouse of all kinds of material desires. Unless one is fully absorbed in Kṛṣṇa consciousness, material desires will come and go. That is the nature of the mind—thinking, feeling and willing. As long as the mind is not engaged in meditation on the lotus feet of the Supreme Personality of Godhead, Kṛṣṇa, the mind will desire so many material enjoyments. Sensual images are recorded in the mind in chronological order, and they become manifest one after another; therefore the living entity has to accept one body after another.
(Srimad Bhagavatam---4:29:68---purport).

The nature of the mind is flickering. Sometimes it accepts something, and immediately it rejects the same thing. Accepting and rejecting is the process of the mind in contact with the five objects of sense gratification—form, taste, smell, sound and touch. In its speculative way, the mind comes in touch with the objects of sense gratification, and when the living entity desires a particular type of body, he gets it. Therefore, the body is an offering by the laws of material nature. The living entity accepts a body and comes out again into the material world to enjoy or suffer according to the construction of the body. Unless we have a particular type of body, we cannot enjoy or suffer according to our mental proclivities inherited from the previous life. The particular type of body is actually offered to us according to our mental condition at the time of death."
(Krsna Book).

The mind is restless, turbulent, obstinate and very strong, O Kṛṣṇa, and to subdue it is, it seems to me, more difficult than controlling the wind."
Just as the air or wind cannot be checked by anyone, the two nostrils, situated in one place, enjoy the sense of smell without impediment. When the tongue is present, the mouth continually tastes all kinds of relishable foodstuffs.
(Srimad Bhagavatam---4:29:11---purport).

The difficulty of controlling the obstinate mind, as expressed by Arjuna, is accepted by the Personality of Godhead. But at the same time He suggests that by practice and detachment it is possible. What is that practice? In the present age no one can observe the strict rules and regulations of placing oneself in a sacred place, focusing the mind on the Supersoul, restraining the senses and mind, observing celibacy, remaining alone, etc. By the practice of Kṛṣṇa consciousness, however, one engages in nine types of devotional service to the Lord.
(Bhagavad-Gita---6:35---purport).