I like this video.... it does a good job of telling a story that can be interpreted a few different ways
The top YouTube comment:
I think the woman is his wife, and the younger girl is his wife many years ago. During the party, he's thinking about when he fell in Love with his wife so many years ago. Their connection is now much more stagnant and planned out. He misses their old, free spirited relationship. He doesn't want the old her to slip away. He's still the spontaneous playful type he used to be, but she's becoming too serious. I Love this video because it speaks of a very true progression of most relationships. Never lose sight of what drew you and your partner together in the first place.
Others in the comment section seem to think it the young woman in the video could represent a previous lover who was more free spirited and fun that he had a fling with before meeting his wife