There is no wrong way to draw! you are an excellent artist by the way.
Horses and other equine/bovine etc creatures are kinda weird. There bones are funky anyway here are my tips.
-Try to keep to the center of the canvas (unless there's a reason to move it away from the center of coarse), don't be afraid to move things around as needed, shrink or grow parts using the select tool. This will give you the most space to work.
- Use simple shapes such as circles, squares, triangles, ovals, etc to break up your subject to make them easier to draw. the more you draw the subject the less you'll need to use these shapes thanks to muscle memory.
-- subtip focusing these circles on joints to help you remember what can move and what can't to help avoid impossible poses or awkward anatomy.
- Draw what isn't there. you will erase it yes, but it will help you find the placement of what is there, such as the heel of the back horses leg and will give you a perspective of where to place it in the future drawings.
-watch horse videos on youtube, or look up pictures of horses to get an idea of movement and anatomy.
- Exaggeration is okay! if you like to simplify things like making the legs noodles, or giant ears (MLP for example is a good use of simplifying but still identifying as a horse). As long as your having fun drawing the horse.
these aren't required by any means, but they may help. Don't be afraid to ask me for anything.