Prabhupada explains that material prosperity (wealth, education, etc.), are external symptoms, just as a fever is the external symptom of an unhealthy body. If one has a fever, and if you want him to become healthy, then you must bring the symptoms of the fever down. Similarly, for these different symptoms of material prosperity to come down, Krishna can take it all away, or we can use it in Krishna's service—yukta-vairagya. By using things for the service of the Lord, the fever will come down. In this way, we can try to become spiritually healthy, and that will be our process of expansion. We need more and more spiritually healthy devotees who can go out and preach and show by their example what it means to be Krishna conscious. Krishna consciousness will then expand unlimitedly. I ask you all to please help spread the mission of Krishna consciousness. Become fixed up devotees in Krishna consciousness and go out and make others Krishna conscious. Make your life successful, and at the same time make others’ lives successful. You will become happy, and they will become happy.
(Lectures from a disciple, Vol 3, Expansion of Krishna Consciousness , Pg 392, 2nd and 4th Paragraph)