It may be a diagnose-able issue :) but I was a wreck (literally) when I first started driving because I would lose focus on the road.
Manual transmission, it seems to me, gives me a far better "feel" for the current state of the car. How fast I'm going, and because I have to change gears it keeps me more focused on the monotony of driving.
So far in my recent search I've been reluctant to even consider an automatic transmission because of what may or may not be just a psychological crutch.