I made peace with the fact that I'm a novelist long ago. Everything I write turns into a novel, whether I intend it to or not. I am notoriously unable to write a succesful short story. I've tried--oh how I've tried! I still struggle with it because I would love to have more publishing credentials in the big-name literary magazines. It's very hard to just put a new novel "out there" with no name that is recognizable, and most writers build their credentials with journal publications. I've tried sending self-contained excerpts of my novels to the journals that accept them, but evidently the excerpts are never quite "self-contained" enough, as one editor recently wrote me back and said "This story feels too much like a novel; there's just too much going on."
I know that a lot of novelists have taken this route. You'll often see something in the acknowledgements like, "Chapter so-and-so first appeared, in slightly altered form, in The Atlantic Monthly as (insert title)." I guess the real question to ask is, just how "altered" is slightly altered?
I guess it might behoove me to do some research in comparison and contrast.
Sorry for getting off-topic, but anyway, I was pretty much branded a novelist in my MFA program when even the shortest works I turned in tended to be over 30 pages in length. My instructor said it's nothing to be ashamed of. She said some of us are simply born to be story writers, and some of us are born to be novelists. I felt a lot better after that conversation. I think a lot of it has to do with how a writer looks at a story. Short story writers have the ability to hone in on the single moment, the single piece that is an intricate part of the whole. Novelists, on the other hand, want to stand back and look at the whole, bigger picture. Or in other words, short story writers (and poets) are more concerned with the parts, and the novelist with the whole, if that makes sense. But good writing, of course, is really all about both--it's simply a matter of what we choose to leave in, and to leave out.