Just as a mirror, which reflects all things, is set in its own container, so too the rational soul is placed in the fragile container of the body. In this way, the body is governed in its earthly life by the soul, and the soul contemplates heavenly things through faith.
You feel the music needs something but you don't know what. So you start searching, fitting, measuring, trying. Every time you try another angle. And sometimes that's frustrating, especially if you don't come up with something for three days.