My timeline isn't unlike williemeikle's, except I've come full circle.
Age 6: I want to be a writer! Wait, no. Maybe an Olympic swimmer. Or a ballerina.
Age 8: OK, I suck at those things. Definitely WRITER.
Age 12: I'm gonna be an actress and meet (possibly marry?) Harrison Ford!
Age 18: Errrr, maybe a career as an academic is more practical. I like writing about books! And I can write my own at the same time!
Age 35, three degrees later: Nope. Not happening. Four courses per semester at adjunct pay rates doesn't leave time to write fiction, plus it's highway robbery.
Age 38: Hey, people will pay me for writing! Too bad it's not fiction. But I finally have time to get serious about writing and studying the market now.
This year: For the first time ever, I make money writing fiction.
Still haven't met Harrison Ford.