When was the song IT'S NOT WHERE YOU START IT'S WHERE YOU FINISH performed during the show?
What is the song thuroughly about?

The musical is Seesaw.
The song you are talking about is the 4th song in Act II.

Here is more info:
Seesaw (musical) - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Seesaw_%28musical%29)