I was doing a reading for someone. She will have a transiting Saturn making a square over her Mercury next year. I explained to her that the influences that she's likely to experience next year would be along the lines of seriousness, being focused, working hard, being cautious, all so that she can consolidate and build her position, especially when it comes to her mind, communication and possibly involving studies or learning a new skill. She exclaimed that those words describe her "That's me!"
True enough, I glanced at her natal chart and noticed the Mercury square Saturn aspect! She doesn't need a transit to experience Saturn square Mercury. She's been experiencing it her whole life! We can surmise that the transit next year is unlikely to have a massive impact on her. But it could be a case where Saturn may find any "loose ends" of her mind to work on.
Which brings us to the fundamental rule when interpreting transits - what does the natal chart say? What's the person's personal reality?