Daniel 5:19 (ESV)

19 And because of the greatness that he gave him, all peoples, nations, and languages trembled and feared before him. Whom he would, he killed, and whom he would, he kept alive; whom he would, he raised up, and whom he would, he humbled.

In the same way that Belshazzar viewed him, Nebuchadnezzar was also inclined to view himself. Whenever he looked at his own power and wealth, he was tempted to exalt himself. It seemed that he could do whatever he wanted: an absolute ruler with all the power.