Yoga means to link oneself with God (Krishna) by concentrating the mind on Him and controlling the ever-disturbing senses. By the practice of yoga one gradually becomes free from materialistic attachments. This is the primary characteristic of the yoga process. When one is free of materialistic attachments one loses interest in the body and becomes interested in spiritual perfection.
By the perfect practice of yoga one becomes completely happy in this life and, after death, one reaches the state of eternal happiness called liberation. In the perfect stage of yoga one is liberated from the cycle of material suffering (see Karma and Reincarnation) and goes to the spiritual world to serve God in perfect purity.
Yoga includes different practices depending on ones level of spiritual advancement, and can be compared to a ladder for attaining the topmost spiritual realisation. The complete ladder is called yoga and may be divided into 3 main parts. 1) Karma, 2) Jnana, and 3) Bhakti.
1) Karma-yoga When a person knows the goal of life is Krishna (God), but is attached to working to get material comforts, then he is acting in karma-yoga.
2) Jnana-yoga When he knows the goal is Krishna, but takes pleasure in mental speculation, he is acting in jnana-yoga.
3) Bhakti-yoga When he knows the goal is Krishna and is not attached to any material thing, either gross or subtle, but simply desires to work for the pleasure of Krishna, then he is acting in bhakti-yoga. This is the highest perfection of the yoga system.
To make yoga practice really successful it requires self restraint (see Principles). The yoga process that the devotees of Krishna practice and endeavour to perfect is in the line of bhakti-yoga.
In the Bhagavad-gita Lord Krishna describes the process of yoga in Krishna consciousness:
"Always chanting my glories, endeavouring with great determination, bowing down before Me, these great souls perpetually worship Me with devotion." (Bhagavad-gita 9.14)
Here it is said that in the practice of bhakti-yoga (Krishna consciousness) one should chant the glories of God.