I've figured out that part of the fear is what I'm only partially aware that I'm telling myself.

"When you're driving, you can't make mistakes. Ever. Because any mistake you make can be deadly."

It's true that mistakes can be deadly, but if I'm paying attention, I'm not likely to make one that big. But it isn't true that there is no room for mistakes. Missing an exit is a mistake, but it probably wouldn't do any more than inconvenience me.