Just like with any other thing you want to master, the drawing requires incredible amount of practice.
The photograph that follows is the same drawing, done by me, two years apart. The one on the left I drew as one of my first drawings ever in 2011 and the one on the right was drawn in 2013.
I did not intentionally work on anything in particular, but since I loved the photograph I used as a model, and I didn’t feel like I have done it enough justice, I decided to draw it again.
Who said that, if it is work and self perfecting you can’t have fun with it?