Nice portrait here.
I can't give any good advice on digital painting, but to me it still has too much of that clean digital look, especially the skin and hair.
Unless this is what you looked for, you may try some more texturing or use different brushes on it.
Again, I have quite the same problem, always trying to refine more and more until it turns into something miles away from what I intended at first.
Keep up the good work!!