In his first letter, the Apostle Peter twice refers to Christians as "aliens" on the earth. Given that Peter also believed Jesus had become King of the planet and that Christians are citizens of the new Kingdom Jesus inaugurated, his use of the word "alien" seems a bit confusing.
But Peter is not confused. Jesus described the Kingdom several times as something that would begin small and grow into something that would fill the whole earth. He also explained to Peter that as children of the Kingdom, we we have a great deal of freedom here that we cannot exercise because most people do not understand the new order and would get upset if we made full use of our freedom. Peter picks up on this theme in his letter as he advises his readers on how to live in a fallen world.
The point is that even though the Kingdom is here and growing, it has not yet filled the earth. Consequently, we stand in the minority and have not overturned enough of the world system to be considered its rightful citizens. The Divine Conspiracy, of course, is to do just that. In the mean time, we are the subversives, if you will, working from within the system to bring people into relationship with God where they can be transformed. This is an active work, for which we must prepare ourselves and actively engage in (1Pet.1:13). Our hope is that we will someday we will see the scales shift and we will become the rightful heirs of the world (though it may not be until Jesus returns physically).
As resident aliens, we live in a place of tension: between us and the world, between the visible world system and the invisible Kingdom. We often feel that tension because of who we are and where we live. We resist the world's propensity for living by passion. We look beyond self-interest and self-indulgence. We believe in the unseen realities of the Kingdom. Those to whom Peter wrote even experienced persecution because of their alien status, because they did not belong to the surrounding culture.
So if you ever get the feeling that you do not belong here, rejoice! The world you see with your eyes is not the one you belong to. The longing you feel is for the unseen Kingdom Among Us, that will someday become the norm — the world seen with our very eyes. It is also a world that you have been called to help lay the groundwork for. "Prepare your minds for action" (1:13) and "set your hope fully on the grace to be given you when Jesus Christ is revealed." We will not always feel this alienated. We will find our home.