This passage is unique amongst the Psalms because the refrain "His love endures forever" is repeated throughout all 26 verses of the Psalm. As the British evangelist and theologian Charles Spurgeon points out, "We shall have this [refrain] repeated in every verse of this song, but not once too often." No matter what we give to the Lord or offer Him, He always offers so much more.
One of the aspects of life that is difficult for many is how often our lives change. But the Lord remains faithful in every aspect of His nature. Christ came to earth to rescue us, He will return for us too. There is a great and grand comfort in the enduring and eternal nature of His presence, sovereignty, and His love.
The Lord is Himself goodness. Humanity has witnessed the abundance of His goodness through our Lord's incarnation as the new Adam and His restoration of the world. It is Christ, offered to us freely, that articulates the profound love of the Triune God. "It is most fitting that by visible things the invisible things of God should be made known," declared Thomas Aquinas.
All of the actions, power, and love of the Lord Jesus Christ on earth reflected the Father and how He feels about us. It is evident in the Parable of the Lost Son, when Christ tells us about how our Father in heaven thinks of us: "So he got up and went to his father. But while he was still a long way off, his father saw him and was filled with compassion for him; he ran to his son, threw his arms around him and kissed him." (Luke 15:20)
The Psalm is a great reminder that despite our own sin, evil, and imperfections, the Lord is good, perfect, and unchanging. It takes the attention off of ourselves and our own pride and puts our attention firmly upon the Lord.
Giving thanks to the Lord for all He has accomplished and being humbled by His goodness is a constant reminder that we were made for a unique and divine purpose. When we compare ourselves to the goodness of God we are awestruck by His love and compassion for us. The author of Psalm 136 saw it fit to repeat the refrain 26 times. So when we are going through pain, hardship, facing death, or even suffering, we can always claim the promise that the love of the Lord endures forever.