Here’s what to do:
Take out a blank sheet of paper or open up a word processor where you can type (I prefer the latter because it’s faster).
Write at the top, “What is my true purpose in life?”
Write an answer (any answer) that pops into your head. It doesn’t have to be a complete sentence. A short phrase is fine.
Repeat step 3 until you write the answer that makes you cry. This is your purpose.
http://www.stevepavlina.com/blog/2005/01/how-to-discover-your-life-purpose-in-about-20-minutes/