Near the end, he writes:
My advice is simple. Be careful with your words. You only have so many to use in your upcoming sermon, so choose them wisely. Those words may comprise your very last sermon. Have you considered that?
Yes, I consider that every week.
One of the pastors who was shot and killed while preaching last year reportedly was speaking on "succeeding at work." God rest him and keep his family, and I mean no disrespect for a brother who is enjoying Jesus face to face right now, but I'll be danged if I'm going out like that. Whatever my last sermon is, God willing, it will proclaim the greatness of the gospel and the glory of Jesus. I try to guarantee this by guaranteeing each next sermon proclaims that. If you're a preacher, I hope you will too. Your church needs it more than anything else.
That's not the only (or best) reason for gospel-centered preaching, but it's a good one.