I fell from heaven to hell for you. What do the lyrics mean?

One person has paid a great price for another person or thing. Unforgettable is a song sung by Tang Rui, released on May 4th, 2008, from his album True Love. This lyric means: "For you, my life has undergone tremendous changes, from a good state to a very bad state." Expressed strong emotional changes, because someone or something had a profound impact on themselves, leading to earth-shaking changes in their lives.