Isaiah 14:12-15 illustrates the process of Satan's thinking that led to his fall. Evidently, God had at some point also given him the earth to govern, as this passage shows him ascending to heaven, implying that he must have come from the earth. Isaiah also writes that he had a throne that he desired to exalt over all the “stars”—angels—of God. Revelation 12:4 reveals that a third of the angels were thrown to the earth with him, probably those whom God had earlier given him to assist him with his job on the earth, but Isaiah 14:13 reports that he wanted to rule all the angels, not just a mere third of them.
As God gave him more, Hêlēl's greed grew until he began to conceive thoughts of taking everything for himself, not just the angels, but God's very throne. As several modern translations read, “I will make myself like the Most High.” In essence, he wanted to be God. He deceived himself into thinking he was smart and powerful enough to boot the “Old Man” out and take over ruling all things!
So we see the sins that most describe Satan: vanity, greed, selfishness, self-exaltation, and pride, of course. Who knows how long these sins festered in him before they broke out into action? However long the time, these sins embittered him until he began to plan a coup against the very throne of heaven and to recruit other angels to his cause.