Great job so far! You have seen some of my drawings before and they are far from good, I would be the first to admit that!
Any way, A few tips that make drawing easier for me: First off, you need to "Feel" the horse, understand his personality, make him who he is. Second of all, Like the people above me said, you need to do a quick sketch of the horses outline, don't take 10 hours on the outline. Another thing, I like"Dramatizing" my pictures, like I like drawing Arabians with their dish in their head and I like to make them look... Overly fragile... With a very nice dish in their head dramitizing them a bit. Third of all, Its way easier to look at a picture when starting off, then you can see the shading. So, here is a picture that took me less than 2 minutes. You start off like this, then, slowly erase the circles and shapes and start shading and before you know it you got a master piece. Try drawing Arabs, make them have a personality and a great big dish, make them look natural. One last thing, When the wind is blowing the horses hair doesnt just sit stiffly on them, it has movement, ALWAYS has movement, make the horses "Flow" (I was drawing the picture of the Arabian Stallion photo I uploaded) (Its a random horse off the internet, my favorite when drawing :)