An old preacher once said, "Some pastors were called to ministry and some just went!" Now, I'll admit that there have been times when I walked through dark storms and questioned whether being "in the ministry" was my idea or God's plan for me. In these times, I poured my heart out to God and revisited some basics about "call".
Remembering one's sense of call to pastoral ministry is beneficial. Perhaps God used the influence of another leader or a specific challenge from the Word to initiate your desire for leadership. The important thing to understand is that all subjective experience must yield to the objective criteria of Scripture. To think biblically about calling, the following considerations should be evaluated:  
(1) Desire to serve as an overseer (I Timothy 3:1)
(2) Qualification for eldership (I Timothy 3:1-6;Titus 1:5ff)
(3) Life experience in leadership (I Timothy 3:4-5)
(4) Demonstration of a shepherd's heart (I Peter 5:1-4)
(5) Spiritual giftedness (I Timothy 4:14;Romans 12:3-8)
(6) Formal testing and recognition by spiritual leaders (Titus 1:5,9;Acts 14:23)  
No matter how much one claims a call to ministry, it is possible to disqualify oneself from fulfilling that call. Qualifications and the objective considerations above must take precedence over all professed feelings, experiences and giftedness.
In my interactions with Church leaders, it seems to be increasingly common for pastors to doubt their call to ministry. Another concern consistently associated with these doubts is a feeling of burn out. The pressures of pastoral ministry are often more than an individual feels capable of handling. This reality is further complicated by a prevailing confusion about a pastor's role. Is a pastor a shepherd tending to the needs of a flock or an entrepreneur leading a business that markets a product? Pastors are viewed as spiritual teachers and overseers, biblical scholars, administrators, CEOs, financial advisors, professional counselors and personal friends. Why should burn out in ministry surprise us? Many pastors long for a more defined understanding of their role -for a clearer understanding of God's design for pastoral leadership (see: http://thinkpoint.wordpress.com/2007/04/11/church-leadership-an-overview/).
Along these lines, all Church leaders would benefit from revisiting the Jethro principle: "This is too much work for you; you cannot do it by yourself" (Exodus 18:14-26).  It may be that we know many truths about God's design for leadership but we do not know how to practice them. Sometimes, if we're honest, we are unwilling to practice them because it would require giving up some control or challenging the expectations of people. The desires to micro-manage and/or to be liked by those we lead can become obstacles to fulfilling biblically defined leadership. More later!
________________________________________Steven W. Cornells.cornell@millersvillebiblechurch.org