Psalm 30:7 (ESV)

7 By your favor, O LORD, you made my mountain stand strong; you hid your face; I was dismayed.

David’s illness was a painful reminder to David that God can withhold his favour. He is not obliged to us. Even David needed to be reminded not to take God’s favour for granted. All his hopes and plans were suddenly threatened. Even David, an astute believer, was terrified. You hid your face is a poetic way of saying that the Lord withheld his blessings and protection.