I have set the LORD always before me: because he is at my right hand, I shall not be moved. (Psalm 16:8)
The Psalmist again shows the firmness and stability of his faith. To set God before us is nothing else than to keep all our senses bound and captive, that they may not run out and go astray after any other object. We must look to him with other eyes than those of the flesh, for we shall seldom be able to perceive him unless we elevate our minds above the world; and faith prevents us from turning our back upon him. The meaning, therefore, is, that David kept his mind so intently fixed upon the providence of God, as to be fully persuaded, that whenever any difficulty or distress should befall him, God would be always at hand to assist him.
He adds, also, continually, to show us how he constantly depended upon the assistance of God, so that, amidst the various conflicts with which he was agitated, no fear of danger could make him turn his eyes to any other quarter than to God in search of succor. And thus we ought so to depend upon God as to continue to be fully persuaded of his being near to us, even when he seems to be removed to the greatest distance from us. When we shall have thus turned our eyes towards him, the masks and the vain illusions of this world will no longer deceive us. (Commentaries)