All righty! Time for a critique!
First, I really like the lone feeling of enjoying a sunset all by yourself, apart from the rest of the world of worries and cares. You found the right background to fit with the right stock to make a beautiful combination, and I especially like the hues and colors of the sunrise. The background? Proportion-wise - beautiful!.
Are the white lines around the horse purposely put there? For the look of a “spirit” horse entering paradise? If so, maybe lowering the opacity of the horse would give it that ghostly, intangible feeling. If not, erasing it out will make it look a lot better. Also, if you change the lighting ever so slightly to match the light source from the sunrise, it will really further the perfection of the scene.
I just adore the tail! However, you can further enhance it by giving it some flyaways, to make it look more realistic and give it movement. Same thing with the mane.
But all in all, this is beautiful piece. Keep up the good work, 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.)