On the topic of not fussing over every line and trying to make them all smooth and perfect . . . I certainly consider that to be a very important artistic breakthrough. That's what the sketching I was talking about a while back is all about, actually. Not caring if the lines are pretty or perfect, just getting them down on paper, getting the shape and movement in.
On the topic of sketching, there's another method of sketching that I use in digital art that you might find useful, if you don't use it already. I've heard it called "lineless sketching" or "colored sketching," and it's basically where you take a fairly big brush in your art program of choice, and just start slapping down color. You figure out where the light hits and what the shapes are with the colors and the form of your brushstrokes, rather than with lines. Usually, I use a gradient that matches the general colors that I want the background to be and put that on a background layer, and then make a new layer for the main subject(s), and just start trying to get the shape and color of it down. Then I work at refining those shapes in the same way that I refine the lines of a sketch, only I take this all the way to completion. I use a rectangular brush for this because it makes sharp lines easier, but round brushes work as well.