All righty! Time for a critique!
First off, I really like the way it is so simple, yet breathtakingly deep and meaningful. You really painted the neutral background to fit with the right stock to make a beautiful combination! The hues and colors are also very balanced.
On a closer look, the space between the two front legs seem a bit too wide; a little bit unsettling, as if the horse is ready to topple over. Maybe if you shorten that distance it would help. The back legs are nicely shaped, but the darker shadowy parts seem to make it look ridge and tight. Perhaps if you lighten it ever so slightly, it would soften the approach.
Also, the head looks a tiny bit too big and "heavy" for the neck. However, the delicate features of the Arabian are beautifully brought out. And I just adore the mane and tail!
All in all, this is a gorgeous piece. Keep it up, and you'll improve!
(Note: if I sound too blunt or hard on your work, then just ignore me! This is merely my own personal judgment, and you don't have to subject to my reasonings.)