Drawing with the non dominant hand

2 drawings (Left hand & right hand drawings) of the Amaryllis seedpod

Ebony pencil on Strathmore 11" x 14" drawing paper

A couple of days ago I challenged myself to draw with my non dominant hand - my left hand.
I started on this mini project yesterday morning - drawing of an Amaryllis seedpod.  The process was going well for about 10 minutes, then my hand was getting shaky and tired.  I finally stopped after take a few breaks and a total of 30+ minutes drawing time.  Wondering if the lateral epicondylitis (in short "Tennis elbow") on my left arm was the cause.
During the drawing process, the urge to use my dominant right hand to make corrections was strong.  I had to work hard to make my brain to coordinate with my left hand and to keep my right hand away from the drawing.
Later in the afternoon I started another drawing of the same subject and same materials but with my dominant hand this time, it took 28 minutes non-stop. 
It was quite a challenge drawing with the non dominant hand but a very good exercise.