I love that sketch! The gesture is very express, and would work quite nicely as a finished work. Your proportions seem a bit off, but that can happen when you are working quickly. Short draw times can be very nerve wracking. The best thing that I can suggest is don't think. Try dropping your time down to say 60seconds you literally have no time to think or second guess yourself. Just focus on mark to page, and let your eyes and muscles do the rest. You know how to draw you just need to trust yourself.
