Many writers deal only with fiction. Some live in a poetry world, while others write technical articles and nothing else. As writers, we need to write what we do best and what feels comfortable. It makes life a great deal easier to live in a comfort zone.
But even so, I think there is something to be said for branching out and trying something different. It took me awhile to find out that creative nonfiction was where I did my strongest writing. I began writing children's stories. It seemed a proper fit since I'd been a grade school teacher long, long ago. And I enjoyed writing fiction for kids. Tried adult fiction and I liked that, too, but I had little success in selling it. Same with poetry. It was the creative nonfiction and then nonfiction articles for writers that began to sell. The first thing I ever sold was a nonfiction article for kids.
Did I give up writing the other categories? Absolutely not! I still write the occasional fiction piece or a poem and even a children's story. It's fun and once in awhile, one of them is published.
I remember when John Grisham wrote a book that didn't fit in with all the mystery novels he'd written and I thought to myself Good for you, Doesn't matter what the critics say. I have a feeling he enjoyed stepping out of his niche. His big benefit was that he can get his work published because of his large number of successful books in his past. Most of us don't have that luxury.
I recently wrote an article about the need of staying on an exercise and good nutrtion program forever, not just a few weeks. It was published in The Best Times March 2011 issue. This newspaper is one geared to seniors in the Kansas City area. It's one I've been in before and hope to again. You can read the article at http://www.thebesttimes.org/readings_writings/readers_share/0311_do_this_forever.shtml It's a nonfiction--article not personal essay. With this one, I stayed in my comfort zone.
Try branching out a little and write something new and different. Your first few tries may be something you'll hide away, but keep at it a nd you just might find a new category to write for.