You feed him by your inclinations, by getting praise from people, attention from people, benefits, help, love. Whether these come justly or by injustice, rightfully or not, this ego is never satisfied; it keeps on wanting attention. As a result it begins to rule over the higher faculties of inspirational power, spiritual power, wisdom, reason, justice - all the beautiful faculties. This nafs or ego or Satan (for the ego is Satan) governs all these faculties, and a man cannot become saintly until he has crushed it. The only way to crush it and annihilate it is by starving it. There is no other way than this whatever. The saintly personality cannot come into being until all this is achieved.