So the first medicine which you should be concerned with is to chant Hare Krishna and to become increasingly steady in Krishna Consciousness. Study Bhagavad-gita As It Is and Srimad-Bhagavatam and continue to help your god-brothers in developing Krishna Consciousness. So develop your preaching abilities in this way, and this will be the most successful and appreciated endeavor.
Letter to Upendra dasa, 6 January, 1969