Psalm 61 outlines our desperate need for God, specifically seen in times of sorrow and hardship. David leans upon the rock who will see him through all things. God has proven Himself faithful time after time. Thus, every believer can confidently go before Him in prayer. Christians do not do this out of mere obligation, but out of a love for God. Prayer is one way that we express worship to God. We thank Him for all that He has done and trust the entirety of our lives to Him. If prayer is omitted, then worship is not occuring. David makes this clear in this Psalm.