Have you ever had a thought in your head that was just so overwhelming and thrilling that you could not help but repeat it and repeat it? That seems to be what happened to the psalmist in Psalm 118. While not quite to the level of Psalm 136 (where the 
psalmist repeated this same phrase 26 times), we read five times in Psalm 118, “His mercy endures forever” (v. 1, 2, 3, 4, 29). The magnitude of that thought led the writer to repeat other phrases as his response.
Twice he said, “Oh, give thanks to the Lord” (v. 1, 29). Twice he said, “It is better to trust in the Lord than to put confidence in man” (v. 8, 9). Three times he said, “In the name of the Lord I will…” (v. 10, 11, 12). Three times he said, “I will praise You” (v. 19, 21, 28).
Has the thought, the reality and the awe-inspiring truth that “God’s mercy endures forever” so saturated your heart and mind and soul that you can’t help but repeat it often, give thanks to the Lord continually, trust in Him fully and praise Him incessantly? If not, why not? — DS