When Lord Jesus Christ also preached God consciousness, only a few followers were there, and still, he had to sacrifice his life. But he was never disappointed. That should be attitude of the preacher. People may accept it or not accept it, we should go on. Because if Krishna is satisfied, if Krishna sees, "Oh, these boys are doing very nice. They are trying their best to preach," that is your reward. That's all.
Reference: Lecture on: Bhagavad-gita 3.18-30 — December 30, 1968, Los Angeles