Moksa Opadesa Yoga: Bhagavad Gita Chapter 18 [Final Revelations of the Ultimate Truth]
Krishna Said > Shaloka: 33
O son of Prtha, that determination which is unbreakable, which is sustained with steadfastness by yoga practice, and thus controls the mind, life, and the acts of the senses, is in the mode of goodness.
Yoga is a means to understand the Supreme Soul. One who is steadily fixed in the Supreme Soul with determination, concentrating one’s mind, life and sensual activities on the Supreme, engages in Krishna consciousness. That sort of determination is in the mode of goodness. The word avyabhicarinya is very significant, for it refers to persons who are engaged in Krishna consciousness and are never deviated by any other activity.