Every musician knows the importance of rehearsals: great performances don't just happen. Likewise, every minister knows the importance of preparation; great sermons don't just happen either. Careful preparation and practice are essential before these and other ingredients are ready to be presented in worship.
The importance of this care is obvious. In worship, God is our true audience—and he certainly has a right to our very best. As a searcher of hearts, he knows when our performance and motivation are second-rate.