Mental activities under the influence of material nature cause happiness and distress within the material world. Being covered by illusion, the living entity eternally continues conditioned life under different designations. Such living entities are known as nitya-baddha, eternally conditioned. On the whole, the mind is the cause of conditioned life; therefore the entire yogic process is meant to control the mind and the senses. If the mind is controlled, the senses are automatically controlled, and therefore the soul is saved from the reactions of pious and impious activity. If the mind is engaged at the lotus feet of Lord Krsna (sa vai manah krsna-padaravindayoh), the senses are automatically engaged in the Lords service. When the mind and senses are engaged in devotional service, the living entity naturally becomes Krsna conscious. As soon as one always thinks of Krsna, he becomes a perfect yogi, as confirmed in Bhagavad-gita (yoginam api sarvesam mad-gatenantaratmana [Bg. 6.47]). This antaratma, the mind, is conditioned by material nature. As stated here, maya-racitantaratma sva-dehinam samsrti-cakra-kutah: the mind, being most powerful, covers the living entity and puts him in the waves of material existence.