As an abstract drawing I actually find this phenomenal. I love what you did with the head and mouth. In the context of the lesson, I think you're spot on with your self assessment. On your next go, think about how each piece inserts into the main form of the body. There are some connections in your drawing that look a bit out of place to me, the neck being the main one. I see it as being more centered on the torso in the reference image. And it does feel stiff, so try to incorporate a bit more gestural curve into some of those lines and that will help give your drawing more life. Again though, this is a really groovy drawing. Keep up the good work!