It's strange. This has happened in a number of lucid dreams I've had(about six or seven total, since February), where I really want to do something productive with my dreams, like solving problems I face daily or learning how to fly(something I really want to do, but haven't had the chance). For instance, I had one last night, in which I had become lucid and finished the course of the current dream. Afterwards, I was satisfied by finishing it, and said to myself, "what next?" Of course, I could have done something productive, but unfortunately, the first thing that came to mind was sex, and it was a downward spiral from there. I tried some last-ditch efforts to save the dream(ie. spinning) but to no avail.
It's happened multiple times, and it's spoiled the dream. Suggestions?