Interesting
Very intense-feeling. I thought more of energy than sadness, though, perhaps by the way the colors are moving. I thought of a rushing wolf or a swooping bird.
I can see why you'd use shades of just one color, but if you'd moved around a bit (used a bluer or redder variant of the same general color) you could have made the picture a bit more dynamic, add another layer of interest...
I still like it, though. Interesting, and kind of thought provoking...