If you just can stop yourself from

如果你已经不能控制

Once, everyday: thinking of me;
每天想我一次

If, because of who I am, you are honest;
如果你因为我而诚实

If you watch my movie,
如果你看我的电影

Listen to my favorite CD;
听我爱的cd

If you can bring me around the world with you;
如果你能带我一起旅行

If you decide to follow your heart,
如果你决定跟随感觉

Strengthen your courage for love;
为爱勇敢一次

If you say that we have each other;
如果你说我们有彼此

If you'll start to believe
如果你会开始相信

This love story;
这般恋爱心情

If you can give me a story of 'what if'.
如果你能给我如果的事

I only want a story of 'what if'.
我只要你一件如果的事

I'll love you with all I've got.
我会奋不顾身地去爱你

(my translation; not direct)