As an English major in college, I had plenty of opportunity to flex my creative writing muscle. Trouble is, I'm a weakling in this area. No matter how hard I tried, the best I could do was mediocre. And nao one wants to read fiction that is merely fair. It wasn't the writing itself I had trouble with; it was the development of a compelling story.
I've always thought of myself as someone who has a healthy imagination. But when faced with a blank page (or screen), I have a very difficult time coming up with a narrative from scratch. Story and character development is an art form. Not everyone can do it well. What I was good, no great, at in college was analyzing literature. I rocked that. Interpreting and dissecting the work of others was my thing.
There is something to be said for pushing yourself. Going beyond your limits. Developing new skills. But an essential aspect of good writing is understanding and respecting your strengths and weaknesses.
Another critical component is being passionate about your subject. If you don't love what you are writing about, it comes through on the page. I never developed any characters I felt that way about. I could spend endless hours trying to force out a piece of fiction. But it wouldn't be honest or sincere. I wouldn't feel it. So it wouldn't be very good.
Sharing my personal experiences as a way of touching and helping others has been my greatest delight, and therefore strength. And that has been the key to my success. It was the inspiration for my first book, and is now for my second. (I even have a third book idea I can't wait to develop.)
And that is why I write nonfiction.