Charles J. Brown gives some sage advice in his book, The Ministry: Addresses to Students of Divinity
Then, more specifically, first, let there be no mechanical observing of any fixed and unvarying method in the preacher’s outlines. An endless variety will naturally arise here from the character of the text and of the theme, which ought ever to guide, as to his specific plan.
In general, the text dictates not only the content of the sermon, it also dictates the structure. Brown doesn’t go into it, but there are two real dangers to that mechanical observation of a fixed and unvarying method (however excellent it may seem) in outlining.
One is the danger of boredom. When you have the same outline every week, it makes the content seem very similar. But more than that, it tends to impose a similarity of content as well. So there is an appearance of similar content, and there is also a reality. Having always the same sort of outline works to keep you from seeing in the text anything that doesn’t square with your outlining, or at least keeps you from using whatever more you saw in your sermon. Your principle of selection is influenced by your outline: if your outline is always the same, your principle of selection is always the same, and so your content varies very little. And thus your preaching becomes very boring.
The other danger is that of undermining the force of your message with an inappropriate outline. A sermon on the doctrine of adoption, for instance, that has the structure of a harangue is a sermon that has lost much of its rhetorical force. Or there are sermons that have an imperatival structure, an “every Christian must _______” method of organization, and yet the content is of grace, an announcement that God in Christ has done. The structure in that case puts the emphasis on the hearer’s responsibility, on their duty, though the theme and focus of the message may be on the grace of God. There again, the structure undermines the content.
Combine these two factors, and a sermon on the reasons Christians have for joy can become a depressing monologue that leaves a congregation drained and clubbed down by the very content that should have rejoiced their hearts and strengthened their hands.