/ic/ - Artwork/Critique

I drew my hand (my fingers are short in reality too) with a 15 minute timelimit to prove to somebody who only drew Disney style cartoons that I was better at them at art despite never drawing anything since school. I drew this about 5 years ago and I have not drawn anything else since.

I suck at pen control (I only learned how to hold a pen correctly as an adult), but I find drawing what I see fairly easy. Should I just grind straight lines/curves for a few days? Is drawing with arm and shoulder muscles really worth doing?