Due to his desire to lord it over material nature, he is put into such undesirable circumstances. Under the influence of material desire, the entity is born sometimes as a demigod, sometimes as a man, sometimes as a beast, as a bird, as a worm, as an aquatic, as a saintly man, as a bug. And in all cases the living entity thinks himself to be the master of his circumstances, yet he is under the influence of material nature.
One has to rise, therefore, above the three material modes and become situated in the transcendental position. That is called Krishna consciousness. Unless one is situated in Krishna consciousness, his material consciousness will oblige him to transfer from one body to another because he has material desires since time immemorial.
The living entity, if he submits to this hearing process, will lose his long-cherished desire to dominate material nature, and gradually and proportionately, as he reduces his long desire to dominate, he comes to enjoy spiritual happiness.
Compiled from Teachings of Srila Prabhupada