I had a weird dream the other day. I dreamt that I was sitting in a college lecture class with my sister. Then I was on line in class and I left the line to pick up my textbook which was at my seat but I picked up the wrong book which belonged to somebody else. So I walked over to get my real book and then I forgot where to put the textbook which wasn't mine so I left it on an empty seat. Then I walked out of the classroom and felt someone following me which was Garrett. Garrett was somebody I knew in high school who I liked and who I never got to know well. Then the dream ended.
Good morning, Joan.
Your dream reminds me of choices and regrets. When you pick up the textbook that belongs to someone else, I think of choosing someone else's path through life. Possibly you have felt obligated to make the same choices that you sister has made, since it is she you are in class with - or maybe you are both being pressured into choices that are not necessarily your own.
In your dream, you realize your mistake and get your own book. If you haven't already decided to make your own life-choices, then this is a message that you should do so. It really doesn't matter who the other book belongs to - someone else can take that path, and they should know it for their own, so it's okay to leave it on an empty seat.
Being followed by Garrett seems like a regret, to me - you never got to know him well, though you would have liked to. If you don't start making your own decisions, you may be followed by many more regrets.