Why is singing my heart will go on so difficult?

My sister and I have been planning an act for a talent show with a duet version of my heart will go on and we sound like really bad, I run out of steam at the end of long phrases and sound muffled and the crashendo parts where they are supposed to be belted sound like kind of awful. Furthermore the harmonies are... show more My sister and I have been planning an act for a talent show with a duet version of my heart will go on and we sound like really bad,

I run out of steam at the end of long phrases and sound muffled and the crashendo parts where they are supposed to be belted sound like kind of awful.

Furthermore the harmonies are not nice sounding and sound like conflicting and such?

What is the case here, and is my heart will go on an easy song? What is wrong? How do we sound better?
7 answers 7