I believe there are two types of Pastors. One I call the "Good Shepherd" Pastor and the other I call the "Little Bo Peep" Pastor.
The "Good Shepherd" Pastor is like the leader Jesus talks about in the Bible. When one of his flock wanders away he immediately leaves the 99 and goes after the one. He finds that one and returns with him to the safety of the flock. This Pastor knows that He is responsible for the souls he has been put in charge of. When one of his church members leaves the church, he goes after that member and finds out what the problem was and comes back to the church with the member in company. Most of the time, just knowing that the Pastor notices and cares about their leaving wins back that member.
The "Little Bo Peep" Pastor is like the one mentioned in the nursery rhyme who says "Leave them alone and they'll come home, wagging their tails behind them". This Pastor says things like "I won't beg anybody to go to my church" and "I guess they never were real members anyway, else they wouldn't have left us". This Pastor never checks to see what the problem was, or if indeed there was a problem, or if maybe that church member just lost his way. The Pastor stays home, safe with the 99 and the one is on his own.
We have too many "Little Bo Peep" Pastors these days. They are content to stay home with the 99 or 98 or even 97 rather than bother with chasing after the errant one or two or three. Everyone wants to be wanted and appreciated and, especially with our "mega-churches" these days, confused and/or hurt people are falling through the cracks and being forgotten. Just a call to say "We miss you" or "Is something wrong?" may solve the problem.
Pastor..... you are responsible for all your sheep, the easy ones and the hard ones. You may have one that leaves and you can't get him to come home, but it is your duty to try.