My comfort zone is spacious so I usually don’t find myself very limited. I have my grade school and high school English teachers to thank for that. They made me write many different types of fiction over the years. Thanks to them I don’t feel a lot of fear about branching out.
If I want to write something, I do. I don’t feel limited. However, I find I prefer certain types of books. I gravitate toward them and avoid others. Fantasy, Historical, Contemporary (m/f, m/m and ménage), I write them all.
That’s a lot of material to fit in one comfort zone.
It’s also not always easy. For example, writing BDSM didn’t come without hours and hours and hundreds of pages of research. By the time I started writing serious BDSM stories (instead of light kink) I was well versed in the techniques and mindsets of the participants. The same goes with ménage. Hours of research.
For me, understanding and knowledge define my comfort zone. If I’m writing fantasy, I thoroughly flesh-out the world. If I’m writing a historical, BDSM, ménage, etc., I do the research necessary for me to feel well-versed in the subject. That’s my best advice for anyone who wants to try writing in an area where they feel unsure. Learn the subject. Make it yours. And you’ll feel right at home.