Not until I tried to sing this song did I realize that it's very difficult.. Many portions of the song require you to sustain your voice in a high pitch for a long time (~__~ ) But it's a really good song :)
Updates: There's one line in the lyrics that I like a lot:
You are the one who makes me happiest, but you also are the one who makes me the saddest.
The person whom you love the most is the one who can hurt you the most, isn't that so true?