他久居你心不知我视你如命
[tā jiŭ jū nĭ xīn bù zhī wŏ shì nĭ rú mìng]
This means 'He has lived in your heart for a long time, but he does not know that I regard you as my life.' It reflects deep devotion where the user is completely devoted to someone, even if that person is unaware of it.