I agree with Cheval and you also need to give the horse more muscle on the shoulder. It looks very weak and not completely attached. I really like the hind-quarters though. Were you working off a picture or doing it by memory?
Sorta both I would just quickly look at it then try and draw it I know I should have studied it a little more but then the rest I sorta forgot to look at the picture xD thanks for the reply :) lol if I draw another one ill post it to see if i've improved any
When you are stuck on what is wrong with a drawing I have had my art professors tell me to look at the work upside down in a mirror. This detaches you from your drawing a bit (if you have ever drawn something and thought it was fantastic and then come back to look at it a couple months later and went yuck! Then you know what I mean by being detached) and a different view sometimes lets you see what you couldn't before.