When one's mind is attached to Krishna, one can fulfill the mission of life in one human birth. If one misses this opportunity, one does not know where he is going, how long he will remain in the cycle of birth and death and when he will achieve the human form of life and the chance to return home, back to Godhead. The most intelligent person, therefore, uses every moment of his life to render loving service to the Lord.
The servants of the Lord are actually the servants of society. They are interested in imparting knowledge of the relationship of the living being with the Supreme Lord, the activities in that transcendental relationship and the ultimate goal of human life. That is the real knowledge which can help society achieve the real aim of human welfare.
Without becoming a devotee of the Lord, one cannot perfect one's human life. The perfection of human life is to be elevated to the spiritual world, where there is no birth, no death, no disease and no old age. Without this aim, any amount of material advancement in so-called comforts can only bring the defeat of the human form of life.
Devotee should only serve the Supreme Personality of Godhead. As Lord is the protector of His Devotees, he takes care of everything. Devotee has nothing to worry about.