What is my purpose?

Every now and again, I enjoy introspecting.  Today I came across the question, "Why I am I here?  What is my purpose?"  I can't answer this question.  Was it the time I was sitting in the parking lot of a bank and noticed the little car next to me start to roll down the hill?  So I hopped out and held the car in place, until the driver came out.  It saved the car from crashing into the cars below.  I don't identify myself as daughter, wife, mother, sales associate, martial artist.  All these can change in a moment's time.  I remember the old Baltimore Catechism question, Why did God make me?  To know Him, love Him, serve Him , so that we could be happy in this world and the next.  Maybe not exact, but close enough.  So I'm right back where I started.