Regarding other yoga exercises, if you take Krishna prasadam you shall keep your body automatically fit for working, so there is no need of extra exercises which are required by persons who may eat more than what is required. So for prosecuting Krishna Consciousness one should not eat more than what is needed. One should not endeavor beyond his capacity. One should not talk unnecessarily. One should not stick with some extra regulative principles, nor should one associate with persons who are not in Krishna Consciousness. One should not be too much greedy. What one should do is chant the Holy Name of the Lord with faith, enthusiasm, and firm conviction on the statement of Lord Caitanya that simply by chanting the Maha Mantra one can be gradually elevated to the highest platform of spiritual perfection. Also what is important is to follow the four regulative principles of avoiding all illicit sexual connections, meat-eating, intoxication and gambling.
Letter to Kanupriya das Brahmacari, 15 January, 1969