It is very easy to let past sermons influence your next sermon. The way a passage is traditionally handled can easily become the default way we feel it should be handled again.
Now there is a positive side to this. If a passage is traditionally handled accurately and appropriately, then being fresh for the sake of it is not a good idea. Let’s be traditional all day long if that means handling the Word well.
However, sometimes a good traditional approach can overpower an equally appropriate approach to a passage. For instance, recently I preached from Acts 8 and Philip’s encounter with the Ethiopian Eunuch. As I studied the passage I felt some subconscious pressure to do what I have always heard from that narrative – namely, a brief telling of the story and then a lengthy engagement with a longer section of Isaiah 53. After all, it is a great opportunity to make clear to our listeners what was shared with the Ethiopian Eunuch.
But is there another legitimate approach? I felt there was. Specifically, I wanted to engage with what occurred in this particular narrative. By keeping my focus on the passage in Acts 8 more, I was able to look at God’s sovereign initiative in preparing an individual for an encounter with God’s Word, and how that Word may not be immediately clear, but God is able to bring clarity to it, and when He does, that reader discovers that clarity in God’s Word is more about the Who? revealed than some sense of What-To-Do? that we might anticipate. Furthermore, seeing Christ clearly is what leads to life transformation. This sense of God’s dealing with individuals and leading them into His Word to find Christ was a rich and unique subject to ponder.
When we come to a passage, let’s remember that this particular passage is unique. Let’s be aware of how we traditionally hear it presented and be sure that this is the way to go before committing ourselves to it. Recognise that while each passage is saying one thing, it is possible to engage each passage in various ways, several of which may be completely legitimate.
Biblical Preaching 
Thank you, Peter. Although there is no pericope in the whole Bible which is indispensable to the Gospel and its application, each one contributes something unique to the whole, as you suggest. It is that unique something which I search for when preparing a sermon. Preaching from the RCL on the Sunday after Christmas I addressed the passage about the Boy Jesus in the Temple. In a way, it is a gift, because of its obvious uniqueness. And very helpful was that forgotten hymn (by modern collections): ‘Within the Father’s House, the Son hath found his home…’ If we can find the uniqueness of a passage we are saved from slipping into an accustomed rut, and we will have found a nuance of originality without resorting to gimmickry.