One of the distinctive features of the Hebrew Psalms is a literary device known as parallelism. While less rich a device in the translated English, it nonetheless remains a feature of most of the Psalms, a curious or perhaps sometimes irritating tendency to always be telling us the same thing twice, as if we didn't get it the first time. The Psalmist tends to repeat himself, as if we need to hear a second time so we understand. See what I mean? It can be irritating to be told the same thing twice.
And yet it's not so in the context of poetry because phrases are not being repeated so much as to teach, to emphasize a point, as they are to produce beauty in their cadence, in their appearance as words on a page, in their sound. C.S Lewis, in his book Reflections on the Psalms, declined to ascribe the Psalter a purely didactic function, noting that it seemed "appropriate, almost inevitable, that when that great Imagination [Who]. . . had invented and formed the whole world of Nature, submitted to express Itself in human speech, that speech should sometimes be poetry. For poetry too is a little incarnation, giving body to what had been before invisible and inaudible."
When I hear the parallelism of the Psalms I don't hear the nagging voice of a mother saying "Clean your room. Clean your room. Clean your room. . . NOW," each phrasing louder and more emphatic, but I hear the chorus of a great song of which you never tire, like "I've got a ticket to ride. I said "I've got a ticket to ride." Better than that, you can ride the roads of your city all day, pound the pavement, scratch away at life from your cubicle, and then look out the window and smile, humming "his love endures forever." "His love endures forever." That song never grows old but resonates in the fabric of creation, in the breeze blowing the maple tree outside your open window, in the heat rising from the sidewalks, and in the smile on a cat's face when she greets you at the end of a long day --- that is, that song has parallels in human experience. When we hear that assuring phrase, we instinctively say "Say it again. Tell me again." Just like when we see a great sunset, we still want to see another, and another, and another. In fact, there is such abundant parallelism in Nature, in human relationships, and in our own day-to-day activities that we can see the poetic nature of life itself --- the repetition of putting children to bed at night, almost but not quite the same way every night, or the regularity of meals, sleep, day and night, and so on, all repetitive and yet each not precisely repeatable. (I could be accused here of making a lot of nothing, but I don't think anything in life is insignificant.)
I encourage reading the Psalms aloud and appreciating them as poetry, as audible expressions of the sometimes inarticulable longings of the human heart. The parallelism is there by providential design to heighten the beauty of the form God used to express his truth through very fallible wordsmiths. It's only a visible expression of a godly parallelism in all of life, the repetition of the good, every day. There's great assurance in that, a good rhythm of life, so enjoy the parallelisms of life. Enjoy them.
Now, let me say all that again in a slightly different way. . . .