Ministry has to be one of the more difficult callings in the world, because we are frequently called to fail. Oh no, we are not expected to fail, but we do. We are expected to produce more disciples, to draw people to Jesus Christ, and to enlarge the church (and the church's financial giving to further God's kingdom on earth).
But I think we forget that Jesus failed to convince a whole lot of people who met him in the flesh. How could we be expected to do any better than his track record!? We seem to think that being presented with the Gospel is an easy decision. What we are asking of people, when we introduce them to Christ, is exceedingly difficult! We are asking them to forsake a lot of what makes them happy and comfortable. Even people who nominally claim Christ are (or should be) challenged to reform their thinking and their actions continually. It's called sanctification, and it's not pretty.
So we, who should be bearing Christ, face a lot of rejection. And that can really get to you after awhile. Only people in sales have a thicker skin for being continually told to get lost. A lot of times the rejection is quite subtle. Will Willimon describes the gentle snub that a lot of pastors receive every week: "often [it] takes the form of that at the end of Paul's speech in Acts 17, the polite, urbane, "Well, that was interesting. Yes, very, very interesting. We'll just have to think about that one. Think about it, yes. (We intend to do nothing about it, but we'll think about it.)""*
The nice part is that the kingdom of God actually depends very little on my failure or success. At the end of the day, as inconsequential as it may make me feel in my quest for meaning, the church will rise and fall at the will of God. God's Kingdom will come on earth in God's time. I get the privilege of being a little part of that big plan, but I certainly don't determine whether it will happen or not. Thank God.
*Willimon, Pastor, p. 296.