You will know your purpose because it is the thing you most strongly attempt to avoid, but that never really goes away.
It sits in the back of your mind, haunting you while you go on about your business like it does not exist.
And yet, in spite of all that you do to ignore it, it remains.
It is as constant and true as your heartbeat, but you deny it.
You convince yourself that there are more important things to focus on and more pressing concerns that require your attention.
There is nothing more important and more pressing, however, than your unique purpose.
Get honest and get to work.