Crying in my dreams

I read somewhere that when you dream that you are crying, you actually are crying and not only dreaming about it. Well, last morning I dreamed that I cried. The occasion? I found myself at the entrance of the white building which turned out to be the National Gallery of Art in D.C. My favourite place which, long time ago, I used to visit almost every week. I know perfectly well why I was crying in my dream, and it certainly had nothing to do with the Gallery, but I still wonder how I managed to connect a picture with the feeling of sadness and loss. Workings of our mind are truly mysterious.