The song "月亮代表我的心" (The classic Chinese song "The Moon Represents My Heart") may not be that romantic after all.

1) When there's new moon - there's nothing that can represent your heart, cos there'll be no moon. No heart, actually.
2) Half moon - you are only giving your half heart to your love ones
3) Crescent - you only give less than quarter of your heart

Etc... all the combination you can think of.

So if you buy this song, don't blame your love one for having mood swing.

Good news is, Chinese calendar or the moon in the sky can help you to tell why the swinging (or whatever)