The verse points to the music of Zheng and Wei, melodies that started as novelty and slowly hollowed out a kingdom from the inside. Drawn for a question about romance, this stick is asking you to listen to the actual sound of your relationship right now. Not the version you describe to friends, not the version on your camera roll, but the tone of the last three real conversations. If what comes back is sniping disguised as banter, withdrawal disguised as independence, or excitement that only shows up when something is wrong, the stick is reflecting a standard you have quietly been letting slip.
The fall in the classical story was never sudden. It was a long sequence of small permissions, each one defensible on its own. Your situation likely rhymes with that. Maybe you have been telling yourself the chemistry is enough, or that the chaos is passion, or that you are being too demanding when you ask for basic steadiness. The 下下 grade is not a verdict on the person across from you; it is a mirror held up to what you have been calling acceptable. Underneath the noise, you already know which note is off-key. The stick is only confirming the thing you have been refusing to name out loud.