The preacher’s first and the most important task is to prepare himself, not his sermon. Any man who has been any length in the ministry will agree wholeheartedly with me concerning this. It is something that one has to learn by experience. At first one tends to think that the great thing is to prepare the sermon – and the sermon, as I have been saying, does need most careful preparation. But altogether more important is the preparation of the preacher himself.
Martin Lloyd-Jones: Preaching and Preachers