You could be getting tired of it if you notice:
- A sudden awareness of time.
- An awareness of distractions.
- A tendency to draw from what you know rather than from observation.
If this happens, stop drawing! (at least for the time being anyway.)
The best way to get past this stage is to develop the technique of “focusing”. This is done by capturing the most interesting part of the subject. This plan is best selected ahead of time so you can concentrate on those areas before fatigue sets in.
Developing these chosen areas at the expense of others allows you to conserve your energy and time. Then you can focus on drawing the good stuff that you like.
I focused on the eyes in the drawing above and left the rest a scribble. Below Egon Schiele takes the topic further by focusing entirely on the hands and face.
Will you plan your focus before starting your next drawing? I don’t know what you think, but to me, there is something really appealing about an unfinished drawing.