/ic/ - Artwork/Critique

I'm a beginner very new to drawing. I find drawing lines towards northeast and southwest(assuming north is towards the top of the page) quite comfortable and easy. However, drawing either north/south/northwest/southeast is really challenging as my elbow is not assisting in the motion at all. Is this something I simply have to practice or is it unreasonable to expect my line quality to be equal regardless of direction?

pic related is what i'm talking about with regards to directions