Once having come to devotional service, you should make this your last birth in the material world. Srila Prabhupada would always speak very strongly on this point, that the human form of life is so rare and valuable, as soon as one understands the purpose of life, he should immediately use it for its full potential. So the purpose of human life is go back home back to Godhead and only by Krishna consciousness can it be accomplished.
September 22, 1992, Kaunas