hey man thanks for stopping by my book-
as far as crits - id say on many of your studies ...im assuming you are doing them from ref or model.....the lines seem darker in tone...a bit more confident than in your own personal stuff from imagination.....i would say try to bridge that gap.....if even to mimick the same line strokes you are doing in your studies......the sureness of strokes will catch.
id also suggest doing more planar studies....simple shapes ,volumes.....mastering the box at different angles....just do drills....take a box and tumble it through space on the page...drawing all the different angles...then go onto distortions and pushing other basic shapes into the boxes......
i guarantee two things....
one it will tweak your mind to the point of hair pulling trying to wrap your head around it
and two you will improve many levels in shape understanding....
i still do the drills and its still a challenge for me...a bit easier sometimes