David was in the midst of a trial. He cried out to God for help. He knows that God is faithful and will answer - He's proven that many times before.
His prayer resonates with the fact that he knows God will deliver him from his enemies.
If we really look at this prayer we'll notice that it has certain sections:
The verse we're highlighting is key because it basically summarizes the whole chapter. David is able to ask God to reveal Himself because he trusts Him. God has been faithful to him time and again. He knows that if he asks, God will give him the desires of his heart because of their relationship and the commitment that he had to the Most High.
This prayer is one that we can pray every day: "Show me proof of your unfailing love Abba Father, for I will trust you. Show me the way I should go, for to You I entrust my life."
I've proven it. I've been praying this prayer for about a week now and I'll tell you the enemy has gone out of his way to prove God to be a liar. But God has shown Himself mighty on my behalf. He has sent so many persons and so many things to remind me that He is El Roi - the God Who Sees.
He saw Hagar when she was at her lowest point. He sees me going through my trials and He sees you too. My prayer for you is that God will show you proof of His unfailing love for you.