When God makes us into a new creation, he gives us a new purpose of being his witnesses and his ambassadors to the world. So how do we do that on a practical and tangible basis? Paul instructed the church of Philippi to "work hard to show the evidence of your salvation" (Phil 2:12). This means that we have a part in changing our behaviours and our lives to reveal Jesus to the world.

Changing our habits and our behaviours is hard, but not impossible.

When the Holy Spirit works in our lives to make us a new creation, it leads to a new purpose. Paul describes the big picture of that purpose in 2 Corinthians 5:17-20, but it's still up to us to discern and discover our own personal purpose that will fit within the bigger purpose.