I am reading Keller's insightful and challenging book on preaching and will be posting quotes. This one was encouraging and liberating.
“While the difference between a bad sermon and a good sermon is mainly the responsibility of the preacher, the difference between good preaching and great preaching lies mainly in the work of the Holy Spirit. . . . We should do the work it takes to make our communication good and leave it up to God how and how often he makes it great for the listener.” Timothy Keller, "Preaching: Communicating Faith in an Age of Skepticism", p. 11-12.