you can go much more darker on some places like the hair, eyes, eye brows, base of the nose, etc. and use more contrast with your lighting. The part that gets the most shadows in your face need to be darker as well. I get the feeling that you've done this from a photo. Do not do that. You won't learn anything about form if you're copying from a flat source. Grab a mirror, get a light source, and then start drawing! goodluck.
I actually wasn't going for realistic; I've already erased alot of hard lines that depicted where some harder shadows were before. It's just one of the ways I draw. I do have to work on contrasting though: I never like going too dark.