Have you ever read the original version of The Little Mermaid? If all you know is the Disney version, you'll find the original, written by Hans Christian Andersen, is very different. For one thing, the mermaid's love for the prince is only part of her motivation, and not even the most important part. She wanted to get a soul, and the only way to do that was to marry a human.
And the whole trading her voice for legs thing? Again, that's only part of the story. Sure, she got legs and feet instead of a tail, but there was an ongoing price for those legs:
"Every step she took was as the witch had said it would be, she felt as if treading upon the points of needles or sharp knives; but she bore it willingly, and stepped as lightly by the prince’s side as a soap-bubble, so that he and all who saw her wondered at her graceful-swaying movements."
Can you see why I associate the chorus of Annie Lennox's Walking on Broken Glass with this story?
"I've got so little left to lose
That it feels just like I'm walking on broken glass
Walking on, walking on broken glass
Walking on, walking on broken glass"
(Go read the original Little Mermaid. It's a very different ending, too, but it's a happy one - if you keep in mind what her true goal was.)
Books: The Little Mermaid, Hans Christian Andersen
Music: Walking on Broken Glass, Annie Lennox