This is a question that is pondered by many. Is the Kingdom of God here and now or will it be established at some future time? Am I supposed to have a role? Can I choose one or will God assign me something?
Think of it like this; when you're travelling business class, the airline extends you the privilege of accessing the VIP lounge at the airport while you wait for your flight. But you may choose to go sit in a fast food restaurant instead. As a Christian, the Kingdom of God is your VIP lounge, the world is the restaurant. And we get to choose.