The speaker is complaining, gently, about love songs. Almost every one is about one of two moments: falling for someone or losing them. What gets left out is the part in between, the "during," when two people are actually together and living the relationship day to day.
The poem's shape mirrors this idea. The "during" sits right in the middle of the poem, set off by dashes, as if it's the very spot the speaker says songs never hit. For the speaker, this stretch is the most important because it "sets the mood" and "decides your future." The last lines are the most telling: without the middle, "there's no me and you." The speaker seems to feel that a couple is built from ordinary shared time, not from beginnings or endings.
The mood is quiet, thoughtful, and a little wistful. It reads like a private observation, a sense that something real is being overlooked.