The Purpose Of A Christian

What is the purpose of a Christian? Is it to build the church? If it is what is the purpose of a man and how does it relate to the purpose of a Christian? If the two purposes are incompatible, what does it mean for the church? If there is an interdependence, then how do we fulfill our purpose if we are dependent on the world fulfilling its purpose? Ought not one purpose cancel out the other? How do you know which side you are on as the world and the church divide. Each following their divergent purpose.