I believe it was just before I entered the first or second grade that I had my first migraine, and they've stuck around since.
Which is just so great, because I love being in pain so, so much.
Migraines are pretty much the only thing that can keep me from doing the things I want to do - including writing. The exact scenario happened the other night, preventing me from accomplishing the work I had hoped to do on my novel.
Still, these are the kinds of punches one must roll with. I've learned to stop being tyrannical over word counts, gladly taking an extra couple hundred words one day because I know I'll be at a loss some other time. As long as I write at least a paragraph every day, I know I'm progressing, and that's got to be good enough.
On the other hand, I've still never made use of a character who has migraines, which is something I've meant to do for a while. Not to Marty Stu it up, but just to throw in a great old fashioned foible. Obviously, it would be a pretty shwag defect for an Eldritch Wizard or some such magic-wielder.
So! How about your personal bio-neurological defects? Do you make use of them in the various incarnations of personalities that occur within your stories? How do you overcome the personal/physical limitations that stand in the way of your writing?