Like a lot of people, I find staying on line when cutting can be a pain in the a##! A while back I downloaded Paint.net (free graphics software). When cutting a standard (in the black) pattern I tend to drift even when blade selection, tension, etc. is correct. I tried something different. I took the original pattern and turned it into a "pencil sketch" using Paint. I went from a hog butcher to a surgeon when cutting this way. The improvement in control was amazing. I believe, like target shooting, you pick a spot on the target and aim as opposed to shooting at the whole thing. I believe your brain allows you to focus more on the thin line than a larger black area. Might not work for everyone but it works for me. Added an example...
link...http://www.getpaint.net/index.html