One of the first pieces of advice any writer gets is to “write what you know.” Most writers, at least in the beginning, take this advice very literally. I’ve known more than one horse enthusiast whose portfolio consisted of specs wherein Patrick Jane/ Castle/ Bones/ Horatio Caine discovered illicit activities in the horse racing world that ended in murder. It’s easy to use this advice to become… *puts on sunglasses*… a one trick pony. YEEAAAHH!
The reason writers are told to “write what you know” has nothing to do with saving you time on research. That’s a nice bonus, sure, but chances are you’re going to have to do research anyway. Even lawyers-turned-writers have to research specific case law before writing their scripts, and the truth, although we don’t like to admit it to the TV-watching public, is that the nitty-gritty details don’t usually matter anyway and can even bog down your script. I should clarify: factual details can bog down your script. What you already have from “writing what you know” is a sense of the atmospheric details. Those are what make your script real.
Family members of writers will often complain that everything they say ends up in a script. And it’s true. If you want your characters to seem real, how better than to make them say things you know for a fact that real people have said? It’s great to be a horse-enthusiast-turned-writer, but what you will bring to the table is not necessarily your encyclopedic knowledge of equestrian sports, it’s how people react in competition, how it feels to train for a big event and then lose (or win), and the stories about how people interact within this setting. These are the little things you can add to your scripts that make them real, and you can find a place for them in a lot of different environments.
Family interactions are especially valuable this way, because almost every good story has a family in it. The time Aunt Betty climbed onto a waterbed and couldn’t get off? Use it! The way your baby cousin used to throw food on the floor, then immediately yell “floor’s clean!” and eat it? It’s yours! The horrible things you said to your parents when you were a teenager? They’ll forgive you when you thank them in your acceptance speech. The details may change, but the feelings are universal. And you already know what they sound like.
So by all means, write what you know. Just be aware that you know a lot more than you think you do.