Except for those moments when I wanted to be The Lone Ranger or Zorro (and there were a lot of them--I think it was the masks), mostly I thought I would be an illustrator, and as I got older that got refined into the notion of comic book illustrator. When I was in sixth grade, for a project I wrote up short biographies on about a dozen classical composers, from Bach to Gershwin. Each of these was accompanied by a portrait of the composer in pencil. I'm sure they looked about as good as any sixth grader's drawings, but they were the extra bit beyond what everyone else in the class was doing with their report project. I got praised for the drawings, and so like any kid in that situation, I drew some more.
As I got older, the drawing turned into copying pages of comic books. Of course I had no idea initially that the original pages were larger than the comics, and that was using a ballpoint because I didn't have any awareness yet of technical pens or crowquille pens or anything else like that. But the art drove me to art school, where I might have gone on to work in advertising or something, except that I took a night course in creative writing the last semester of my second year, and some focal shift occurred. I started writing instead of painting. Visually trained, I wrote with imagery even before I'd heard of concepts like "telling details," or scene-versus-summary, or the "fictive dream." The more I wrote, the less I drew and painted, as if I could only hold onto one form of expression or the other. Most drawing that I do now is to represent something to myself from in a novel-in-progress--a character or a setting.
I agree with Ms. L'Engle about the inevitability of vulnerability. One thing I've learned along this journey into the craft of writing and, with it, publication, is that getting published does not make one less sensitive to the doubts and fears--the vulnerability of life. I've seen more than one writer arrive at their big break into publishing thinking that this is going to change their life. Now everything will be better, maybe even perfect. And the book comes out...and nothing happens. They're the same person. They have to get up and go face the laptop screen again and start another book, same as before.
The other thing I've learned is that everybody everywhere is damaged goods. We've all been vulnerable and we've all been stung, hurt, disappointed. For some, irreparably so. Anyone who says "Not me" is either deluded or lives a remarkably hermetic life. Besides, all those things that have happened to us are the raw materials of creation. The way you write about other people is by touching and transforming your own life, your own experiences.
As for the rest of this topic, I'll let you know how things turn out as an adult when I get there, although they'll have to drag me kicking and screaming into adulthood. Preferably after I'm deceased.