What does this mean?

"When you live your dreams you'll find destiny is written in your heart."

You see.... the girls have a "Princess and the Pauper" Barbie that sings this when you push a button on its back. They run around pushing it over and over and singing along with it.

I've tried to figure it out. Not that I really care that much about Barbie's thoughts on dreams and destiny and such..... but I figure sooner or later one of my kids is going to ask me what it means. And to be honest, I haven't got a clue what I'd tell them.

Anyone wanna help me out here?