As long as man is a captive of habit, pursuing the dictates of self and desire, he is vanquished and defeated. This passionate personal ego takes the reins from his hands, crowds out the qualities of the divine ego and changes him into an animal, a creature unable to judge good from evil, or to distinguish light from darkness. He becomes blind to divine attributes, for this acquired individuality, the result of an evil routine of thought becomes the dominant note of his life. May all of you be freed from these dangers and delivered from the world of desires that you may enter into the realm of light and become divine, radiant, merciful, Godlike.
(‘Abdu’l-Bahá, Divine Philosophy, p. 133-134)
What causes the change in the individuality? It comes through the acquirement of evil habits. God originally endowed man with an individuality which enjoyed that which was beneficial and shunned the drug; but man through his evil habits changes this creation and transforms the divine illumination into satanic darkness.
(‘Abdu’l-Bahá, Divine Philosophy, p. 133)