Bai's poem catches a feeling most people know: lying awake at night because someone won't leave your mind. The speaker is stuck in the dark hours, wanting rest but unable to get it. Their thoughts keep running toward another person, and the poem says this happens "at random moments," so there's no pattern to predict or prepare for.
What makes the poem interesting is its last line. The speaker wishes the person would "vanish" from their mind, which sounds almost harsh. But the wish is only about sleep. Nothing in the poem says the speaker wants the person gone from their life, and the pull of those thoughts suggests the opposite. The speaker seems caught between longing and exhaustion, annoyed at being kept awake yet clearly unable to stop thinking.
The mood is quiet, tired, and a little restless. Short, plain lines make it feel like a confession whispered at midnight, honest and unpolished, much like the thoughts themselves.