If a ship is in the ocean without a rudder, it is left without a sense of direction, floating, going whichever way the wind blows. It is not unlike the person without a sense of purpose. Purpose is your rudder in life, it sets the course for the direction that you will head in.
It is not unusual to be overwhelmed with where to start when someone poses the question, “What on earth are you here for?” Each one of us is called to a different purpose, and discovering what yours is may take some time, effort and soul searching to determine. Once you have discovered what your purpose is, write it out in a Mission Statement, it will chart the course for your life and you will be able to measure what you will say “yes” to and what you will steer away from based on how it fits within your Mission Statement.
The following link provides a good foundation to start finding the sense of purpose in your own life. http://www.wikihow.com/Find-Your-Life%27s-Purpose