The following is taken from the book Preaching and Preachers. I love the book and think you should think about this quote:
As it is true to say that there is no such thing as a holiday in the spiritual realm, I always feel that in the same sense the preacher never has a holiday. He has times of absence from his normal work, he has vacations, but because of the nature and character of his calling he is never free from his work. Everything he does, or that happens to him, he finds to be relevant to this great work, and is therefore a part of his preparation.
But turning to certain specific matters, the preacher’s first, and the most important task is to prepare himself, not his sermon. Any man who has been any length of time in the ministry will agree whole heartedly 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.
Martyn Lloyd Jones, Preaching and Preachers