D.A. Carson

"I know pagans who find satisfaction and fulfillment by teaching nuclear physics.  In any Christian view of life, self-fulfillment must never be permitted to become the controlling issue.  The issue is service, the service of real people.  The question is, How can I be most useful?, not, How can I feel most useful?  The goal is, How can I best glorify God by serving his people?, not, How can I feel most comfortable and appreciated while engaging in some acceptable form of Christian ministry?  The assumption is, How shall the Christian service to which God calls me be enhanced by my daily breath, by my principled commitment to take up my cross daily and die?, not, How shall the form of service I am considering enhance my career?  This is not to deny that Christians may derive joy from work honestly offered to God, whether that work is vocational ministry or research into the properties of quarks.  But it is one thing to find joy in the work to which we are called, and another to make joy the goal of life, the fundamental criterion that controls our choices.  It is one thing to weigh a Christian leader's evaluation of our gifts, and another so to focus on our perception of our gifts that self-worship has crept in through the back door.  It is one thing to think of people as a live audience that will appreciate our displays of homiletical prowess, and another that passionately shapes each sermon to convey the truth to God's people for their good."

D.A. Carson, A Call to Spiritual Reformation, p.83