I generally serve small congregations. These congregations often tend to be in difficult situations. They may have very little money in the bank, or have either too few members, too many elderly members, or all of the above. During my time of service with these congregations, I can't count the number of times I've heard the phrase "we can't do that," "we've never done it that way before," or some variant of "that's impossible."
In many cases, I have to agree that for small congregations, the things a church is called to do, such as establishment of local missions, spreading the Good News of the Gospel, i.e. evangelism, or showing the unchurched that Christianity is relevant to their lives, may be improbable. As an interim pastor, I've also looked at some things I am called to do in a congregation, such a reducing conflict levels, convincing congregations in depression that change and hope are possible, or, the hardest task, convincing some congregations of a need for drastic change, and thought to myself, "this is just not going to happen."
Benedict addresses this issue by instructing us to speak up and say that we don't think we can do something. But he also tells us that we are to try anyway and depend on God's grace to help us achieve what we think is impossible. There's an old joke, told by Rev. Lowell Striker, that tells of a pastor who stood up to preach a sermon. The pastor looks out over the congregation and said it was impossible for him to write a sermon so this week he would have to depend on the grace of God. The pastor then promised he would do much better next week.
It is impossible for us to do better than to depend on God's grace. Scripture tells us in Luke 1:37 "nothing is impossible for God." And yes, that is a proof text taken out of context. But the context itself deals with the impossible situation of an angel speaking to a peasant girl and telling her she would give birth to the Messiah. What could be more impossible than that? And yet, it happened.
Some tasks for congregations, and pastors may be impossible. But I do not recall any Scriptural guarantee that we will always succeed. We are, however, called to faithfully try to do God's work. And if you think about it, in the work God calls us to do how can anything we do be a failure. We may never see the results of our efforts. But I truly believe there will be results.
I also hope that congregations would rather work against the odds, even if there is a probability a task God calls them to do will result in an ending to their congregation. I pray they would rather go out in a burning flame that blazes Christ's light into the world's darkness, than to let their light simply fade away and disappear.
Brother Oscar Romero