Wonderfully done. I find shading to be the task that is most complicated, as you have to stay true to one source of light all the time. But this shows greatly how much good shading can add to a picture. You can't help but wonder with this picture what is hidden in those shadows. Is she staring at us? Is she dead? Beautiful! Very atmospheric.
the trick is to become submissive to criticism, never let a tutor or teacher tell you that your good, if you can find a strict teacher then find him/her to work from, if you get upset easily then you will not have room to improve and change your work until you die... delightful huh