mind

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.
 
This practice is called pratyahara, or withdrawing the senses from the sense objects. The sense organs for acquiring knowledge — the eyes, ears, nose, tongue and touch — should be fully controlled and should not be allowed to engage in self-gratification.

In this way the mind focuses on the Supersoul in the heart, and the life force is raised to the top of the head. In the Sixth Chapter this process is described in detail.

But as mentioned before, this practice is not practical in this age. The best process is Krishna consciousness. If one is always able to fix his mind on Krishna in devotional service, it is very easy for him to remain in an undisturbed transcendental trance, or in samadhi.

This perfect stage of self-realization is attained not by artificial means, but under the lotus feet of the Lord, who is always transcendental. In the Bhagavad-gita the Lord says that He is present in everyone's heart, and from Him only all knowledge, remembrance or forgetfulness take place. When the living being desires to be an enjoyer of material energy (illusory phenomena), the Lord covers the living being in the mystery of forgetfulness, and thus the living being misinterprets the gross body and subtle mind to be his own self.

And by culture of transcendental knowledge, when the living being prays to the Lord for deliverance from the clutches of forgetfulness, the Lord, by His causeless mercy, removes the living being's illusory curtain, and thus he realizes his own self. He then engages himself in the service of the Lord in his eternal constitutional position, becoming liberated from the conditioned life. 

This means that perfect self-realization is made possible by the adoption of godly or spiritual life. Self-realization means becoming indifferent to the needs of the gross and subtle bodies and becoming serious about the activities of the self. One's memory of Krishna is revived by chanting the mahä-mantra, Hare Krishna. By this practice of chanting and hearing the sound vibration of the Supreme Lord, one's ear, tongue and mind are engaged. This mystic meditation is very easy to practice, and it helps one attain the Supreme Lord, the original constitutional position of the living entity.