You have to remember the nature of the drawing you made, it was a quick sketch, not a sit down and draw my absolute best and take time. Instead of saying how bad it is you can look at what you did well, and what needs improving in your opinion, comparing the character to, perhaps, a more canon source if you wish. It is hard to not be so hard on yourself, I have that problem very badly myself. Just a few silly suggestions I thought I'd make.