On page 23 of Jack Canfield's book The Success Principles he has an exercise you can do to ferret out a statement about your life's purpose. Here's what I came up with.
My purpose is to give voice to my own and others' life stories through my imagination and creativity in order to create a world of empathy, understanding and joy.
I also noted a number of goals. You are supposed to be very specific as to times and so forth. That creates a goal rather than a good idea. For example a good idea would be to state "I want to publish a book."
I wrote "By July 15th 2007 I will finish revising "A Generous Absence."
"By June 15th 2008, the novel will be published and in the bookstores for sale."
He encourages you to write a "breakthrough" goal. One that will radically change your life when you accomplish it.
By June 15th 2009 my novel will earn $600,000 and the movie rights will be sold for twice that amount. The book will be translated into many languages. : )