"Do you ever get this thing where as soon as you "get somewhere" in the Work, some other part of you seems to take over and back off in fear and force you back? What _is_ that, and how does one get rid of it?"
In my opinion that is the guardian of the threshold. I may have the exact term wrong.
To get past it, you keep learning. I am working on some GD techniques now to get past that. Stay tuned and you just may put some things together that could help.