Process of Elimination

In this portrait I drew, I found myself thinking of the things I could improve while in the process of producing a drawing. Some of the few things I found that I could improve on are these listed below.

Hair quality, practicing techniques to get the hair shadows and values to a visible and at least semi-realistic quality.
Shadowing and shading details that make up the light source of the drawing
Skin complexion, this is a difficult one as it takes a lot of observing the photo being drawn to get down details that makeup shadows or complexions of the person.

I thought about more things I could work:

Time management, taking more time to draw certain details to obtain more realism
Patience, I tend to rush the process too much. I need to practice observing and correlations to what is being seen that can be drawn.

I think that is about it. With time & practice, I think I will get better. Anybody that keeps up with their drawing skills and stays consistent can improve.