@gregmoore I completely relate. I still struggle with it also. It's hard to overcome. I've learned the best strategy for me is to allocate a set amount of time, do the best I can in that time block, and move on. My sketchbooks are filled with half done drawings. But that's fine. You still learn some things for the next drawing. I'm trying to crank out a lot of work and just to push past that inner critic.
I have a friend that completes many more drawings when he just uses single sheets of paper. It was something about not wanting to "mess up" a fancy new sketch book that held him back. Working with single sheets took the pressure off.