"Another exposition of the expression, 'Awake ('urah) my glory.' What is the signification of the phrase 'Urah [lit. "empty"] my glory? It means [that it is of no account] in comparison with the worship of my Creator. For his inclination would tell him: David! Are you not a king? And is it not the practice of kings to sleep until three hours in the day? Yet you are accustomed to rise at midnight! David would answer it: 'Empty is my glory': my glory is of no account whatever in the presence of the glory of my Creator! Consequently it says: ''urah my glory.'
Midrash Rabbah XV. 15-16
inclination i.e., his evil inclination
it: his evil inclination