Stick with what your good at...
but still stick your neck out and try new things.
Fact: I'm not very good at writing fiction. I know this because I wrote a short story that went nowhere and my friends and writing workshop were at least somewhat kind about saying it. I also knew it as I was writing it.
Not Fiction: I'm a pretty good nonfiction writer and the next writing class I take and workshop I go to are going to be developing that skill. My ability to tell a true story is a lot better than making one up.
Writing fiction requires a rich fantasy life and enjoying escapism I think. That's not a criticism of people who are that way, but an observation from being around fiction and screen writers. Movie lovers are like this also. Perhaps they're trying to make sense of the real world by creating a world of make believe. Maybe I'm over-analyzing it or thinking too much about it, a fact that is probably why I'm better at writing nonfiction.
Too me it's much more interesting observing the real world, studying history, looking at factual information and making sense of it and commenting on it. That's just my preference. Thankfully there are people who can write fiction, screen plays, make movies and offer something to escape into for awhile. Real life can often need escaping, occasionally I enjoy doing that. The "a ha" moment in my recent revelation about my lack of fiction writing skills, came when I realized that the fiction I do read are historical novels. Especially ones well researched and grounded in fact.
In order to keep life from being boring, to stretch personal boundaries, requires a creative person to take risks. Nothing ventured, nothing gained. At least I can say I took up a challenge and did it, faced the results, learned from it. Who knows? I may end up writing a historical short story or novel someday.