Confused

During my break I prepared one course. I read a couple of readers and thought about a possible topic I want to write about in my seminar paper. So today was the first time this course took place. And somehow I was confused. The lecturer wrote me an email which said, it is great to start early and know the topic one wants to talk about. Today in class however it sounded totally different. We should have an idea what we would like to do UNTIL next week. And when I asked some questions she told me I had a preconception. How am I supposed to understand that? A couple of weeks ago it was great that I wanted to start early and now out of the blue it is wrong!