It's a good photo but I think more care with regard to little things like keeping the camera level would have helped.
I'd crop way down on this as to me the wedge made by the bottom of the shadow and your dogs paw should occupy much more of the frame. It looks like very bright sunlight, if you're aiming for melancholy I'd try to tone down the strong specular highlights coming off the fur, I'd also dodge and burn round the eye to make it a focal point.
hth
