Our purpose in life as followers of Jesus is (in short) to love God, love people & share the gospel. 

King Saul got his purpose and plan confused - caring more about being the most loved King (the plan for his life) than following God (his purpose).

In contrast, lowly shepherd boy David stayed humble, trusted God and did his best where he was.

We can learn from David and live out our purpose where we are - not going in search of a Goliath moment but making the most out of our current situation and trusting that God has us here for a reason.