Lifting the Fog
The project is a dense fog and if you think about it you'll quickly drift into paralysis by analysis; a state in which you can pretend to be thinking or working but will really be doing neither.
The cure is to take small actions - a bit here and a bit there - that are related to the project's completion. You know this. You've read David Allen's Get It Done, but you probably failed to adopt his entire program so just go with this small slice:
Complete a few small tasks and then a few more.
You'll find that the fog has lifted.