I will tell it in few words:
“Once Upon a time in a deep blue sea in a wonderful crystal palace lived a little mermaid. She was beautiful beyond the words and also she was a very gifted singer. Her voice was charming and unique, no one could sing as her.
On her 15th birthday little mermaid was aloud to swim to the surface of the sea and to see the land.
She swam up, and saw a ship in the storm. The ship was broken and then she saw a prince fighting for his life with waves. Prince was about to drawn, when she rushed to help him and saved his life.
And of course – she felt in love from the first site. She brought the prince to the shore where he was found by some girl.
Little mermaid was happy for him and also very sad because she couldn’t see him anymore. She missed him so much, that she went to a witch and asked her to change her fish tail to human legs.
The witch gave her a magic potion, but not for free. She took the most precious thing the mermaid had – her beautiful voice, and – as that would not be enough – the little mermaid had to suffer enormous pain with each step she makes.
The little mermaid took a potion, got legs, met price, he liked her and was spending a lot of time with her, but - as she was mute – he was not taking her seriously. So she was following him everywhere and entertaining him with her dances even when she had to suffer pain because of that.
But the worst of the worst was that she was cursed to turn into sea foam if her prince will marry another woman.
What happened next?... The prince was invited to a neighborhood kingdom and met there a girl who has found him on the shore. No matter that he went there together with little mermaid, as soon as he saw the other – he has decided to marry her. The poor little mermaid had her heart broken, and turned into sea foam.
The moral of the story is: you should never ever sacrifice your essence for any prince or princess, because you will become a pitiful suffering creature not even able to speak for yourself and the object of your dreams will not appreciate your sacrifice at all and most probably will even marry someone else.