Míngzhī tā bú ài nǐ, hái yìzhí zhuī tā, zhè bú shì fēi'é-pūhuǒ ma?
You know full well he doesn't love you and you keep chasing him. Isn't that flying into the flame?
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Moths drawn to a flame are an old image: the 《梁书》 already has 如飞蛾之赴火 "like a moth going to the fire". In love songs it can sound tragic or even brave; as advice it means "you are destroying yourself".