In chapter 5 of Cornelius Plantinga Jr.'s book Engaging God's world Plantinga discusses vocation. Plantinga explains that each of us has our own life and situations that we have to keep pure and holy. We also have to help others do the same; we cannot just stay in our own little christian bubble. We all have a small kingdom of God that we need to help preserve within the kingdom of God that contains everyone everywhere.
Plantinga tells us that Jesus accomplished a lot in his time here on Earth, but he also left us a lot to do and work on. We all have so much that we can work on during our short time on Earth. Jesus has called us all to lead selfless lives. With all the problems in our self and in the world there is lot to work on in very little time.
Later Plantinga talks about what college should train us for. It should not just train us for our future career, it should prepare us for our living in God's kingdom.