It would not be fair for me or anyone to criticize the decision of a person who leaves the ministry. I do not know what is going on in their lives or in their homes. I do know that the Bible says the gifts and calling of God are without repentence, so I don't believe God changes His mind about whether a person is called to ministry or not. What I believe is that the primary reason that people abandon the ministry after a short period of time is that they lose the passion for what they are doing.
Andrew Blackwood once wrote, "In pastoral work the most serious obstacles lie within a man's soul." That means the battle to remain or leave the ministry lies within us. Ministry is tough and often thankless, and unless a person finds a way to maintain his or her passion for ministry it can become a burden to carry. So, how does one maintain that passion?
First, we must return to our original calling. I found it helpful when things were not going well in ministry to remember God's call on my life. This was not a career I chose for myself; this was a ministry to which I believed God had called me. When I remembered that it became easier for me to remind myself that God could sustain me in this work. For bivocational ministers it's also important to remember that God has called us to this unique ministry. Not everyone can do what we do. Our work and calling is not inferior in any way to that of a fully-funded pastor. It is God's call on our lives to serve this particular place at this particular time. Think about this for a moment: Out of the billions of people God could have called, He chose you to serve in your place of ministry. I find that reflecting on that is both humbling and re-assuring. It strengthens me for the battles and pressures I face, and it helps renew my passion for ministry.
The second thing that we must do is maintain our passion for Jesus Christ. I've written about this elsewhere, but I continue to be amazed at how easy it is for a minister to become so consumed with what he or she is doing that we forget God. We neglect our own spiritual development. We ignore our need for private times of worship and reflection. If we lose our passion for Christ it follows that we will soon lose our passion for the work to which He has called us. We simply must set aside time to strengthen and grow our relationship with Him.
The final thing I'll mention is that we must set aside time for family and for some personal R&R (that's rest and relaxation for all you non-Navy types). If you work a 40 hour week on a job and then spend every waking minute doing ministry, you'll lose your passion for the ministry rather quickly. So will your family. Get a life! Have a date night with your spouse. Enjoy your children while they are growing up and participate in their activities. Make friends with people outside the church and spend time with them When you work, work hard. When you play, have fun and don't worry about the work. If you do that, when you return to work you'll find it much more enjoyable and you'll find it much easier about doing it with passion. For more on this subject you may want to read my book, The Bivocational Pastor: Two Jobs, One Ministry.