This verse is a description of total reliance on God. Just as the eyes of a servant are riveted on his master, our eyes should be directed to and focused on God.
This is how knowledge of His countenance is gained and how God reveals Himself to us (see Isaiah 53:1). Our spiritual strength begins to be drained when we stop lifting our eyes to Him. Our stamina is sapped, not so much through external troubles surrounding us but through problems in our thinking. We wrongfully think, "I suppose I've been stretching myself a little too much, standing too tall and trying to look like God instead of being an ordinary humble person." We have to realize that no effort can be too high.
For example, you came to a crisis in your life, took a stand for God, and even had the witness of the Spirit as a confirmation that what you did was right. But now, maybe weeks or years have gone by, and you are slowly coming to the conclusion- "Well, maybe what I did showed too much pride or was superficial. Was I taking a stand a bit too high for me?" Your "rational" friends come and say, "Don't be silly. We knew when you first talked about this spiritual awakening that it was a passing impulse, that you couldn't hold up under the strain. And anyway, God doesn't expect you to endure." You respond by saying, "Well, I suppose I was expecting too much." That sounds humble to say, but it means that your reliance on God is gone, and you are now relying on worldly opinion. The danger comes when, no longer relying on God, you neglect to focus your eyes on Him. Only when God brings you to a sudden stop will you realize that you have been the loser. Whenever there is a spiritual drain in your life, correct it immediately. Realize that something has been coming between you and God, and change or remove it at once.