Second Samuel 11, the chapter of the Bible I call "David's Lists of Mistakes," begins with, well, David's first mistake of the chapter: "In the spring, at the time when kings go off to war, David sent Joab out with the king's men and the whole Israelite army. They destroyed the Ammonites and beseiged Rabbah. But David remained in Jerusalem." King David was not where he was supposed to be. When kings went to war, he stayed home. Thus his troubles began.
One of the current phrases in leadership studies is "the seats on the bus." For a church to succeed, two things must happen. First, you have to get people on the bus. People have to buy into the church's vision and mission and choose to take part. Second, once they're on the bus, they have to sit in the right seats. Those people have to find and fulfill their purpose in the church. And I do mean their purpose. It won't do anyone any good for a person who can't balance a checkbook to sit in the treasurer's seat. A called preacher doesn't need to sit a cook's seat. Everyone has a seat on the bus, and once they find the one matching their gifts, graces, and calling and sit in it, the bus will run more smoothly, faster, and farther.
Everyone has two callings: a call to become a Christian and a call to a job for the kingdom. We give an invitation at the end of every service mostly for people to answer their first calling. Consider this your invitation to answer your second calling. Come find your seat on the bus. Get where you should be. Live out your calling for the glory of God.