I saw your horse drawing. It's not bad. Good job. But I'm going to tell you something that someone told me and it changed the way I draw forever.
Make it Pop.
Step away from your drawing, about 8 to 10 feet away. And tell me if the drawing looks good from back there. Chances are, the shading is too similar throughout the drawing. This means that from only a few feet away, the contrast isn't strong enough to catch your eye.
Find your Darkest Darks and your Lightest Lights. Decide where the darkest areas will be. Right now, your darkest line is the little ball on the bridal. Is that the focal point? Chances are it isn't, right?
Remember the boldest area with the most contrast will be the focus of a drawing. It's the "loudest" place on a drawing. This can be done with thicker line, darker shading, or by adding the most detail when compared to the rest of the drawing.
It's not always easy to re-work a drawing. Especially when your proud of what you do. But always keep in mind, there will always be more drawings for you to do. So even if you work a drawing too much, or end up scribbling over top of it, you can always draw again.
Good luck, I'd love to see how you really Make it Pop.