I'm not an NTJ, but I can identify with a lot of what you write. I tend to get locked into a comfort zone and stagnate ... not producing anything of real value. It can be a tough cycle to break, since it takes some inertia to get things moving again.
Looking back at successful periods of my life however, I've noticed that they all came when I moved outside of my comfort zone ... either through changes in my environment, or by placing myself in situations where I was forced to act. One huge movement outside of my comfort zone was joining the military. While I don't necessarily recommend that, it did get my butt moving towards multiple goals that I eventually achieved.
Another big movement outside my comfort zone was losing my military career and having nothing to fall back on. I basically didn't know where my next meal was coming from. That got me motivated for grad school, which ended up being a delightful change from the J-based military and a new career.
If you can create some sort of situation that forces you out of your comfort zone, then I believe greater things could start happening for you. Figuring out ways to do that is the trick, however. Perhaps making a promise or committment to somebody or an organization that forces you to follow through ... even a contractual committment. That might get the inertia going. Placing yourself in new situations ... intellectual, work related, social, etc. can also sometimes jump start the move.
Best of luck.