Awww... I know what you mean.
Just watch out that you don't develop a character who becomes something of the evil voice in your head. It's fun, but people think it's strange.
I guess that's one benefit to writing a kid's story. I can see a lot of myself in Katy (and some Teresa in Celestia), but because she's just a kid, I can't become totally identified with her or obsessed with what she's obsessed with.
Not that that couldn't be kinda fun, mind you...