I have noticed that students can be back too far from
their drawing or painting surface. Then your arm tires
quickly and that is not good if you want to be working
for an hour or two. This distance in the photo shows
the art bent, not straight out. This is good!
Also, be sure your work surface is perpendicular to
your line of vision. If you have it slanted back away
from you too much, you will not draw things in