I think this is a fine and elegant composition. Maybe you shouldn't take TOO TOO seriously all that can be written formally about composition because you seem to have a really good sense of it naturally. Still, what has been said above is very good too. Another very important aspect of composition is an interesting variance of the size and shape of things - ie: if everyting is about the same sixe, shape, color etc = boring. There is always the exception to the rules. ALWAYS! For instance in this composition of yours, there are few radical color shifts, but the differences between what is there is really striking and describes subtle nuance and mood. Nice. Go for it!