I also have Asperger's Syndrome, this makes it so complicated. It's like I need an outline for everything to keep me on track.
Heh, I'm pretty sure that 95% of the people that I work with have Asperger's. They're all socially awkward, quirky, quiet, and can sit at a desk in front of a computer screen for 10+ hours a day.
I like to think that I'm the most "normal" guy in the office, but I guess the fact that I'm on this site several times a day probably makes that very unlikely...
But back to your ability to stay focused on a project... I have somewhat the same problem. I've got probably 30 projects or more that I've started and never finished. I usually get far enough along to prove to myself that I "could" finish it if I wanted to, and then I put it down and go work on something else.
I guess that's one reason I decided to start doing OS development -- because there are so many different problems to solve, and an endless list of hardware to support, once I get something working, I can just switch to something else that doesn't work at all.
So, I wouldn't worry about trying to get everything done, because that'll probably never happen. Just spend a few days working on it, and then take a break for a few days and watch some TV or hang out with your family or something to take your mind off of your project for a while. When you come back, you'll probably make more progress than if you had worked on it for 2 weeks straight.
There have been several threads about how to keep from getting "burned out" while working on this type of project that are worth reading, I think. But basically just work on it when you feel like it, and put it away when you don't.
And, show off your progress in the "What does your OS look like" or the "AWWW YEAH!" threads whenever you reach some sort of milestone. That helps with the motivation as well.
Good luck. Let us know if we can help, or if you get stuck on a problem for more than a few hours.