Beginning writers hear this all the time. It's possibly the worst piece of advice out there - but with one little word change, it could become the best advice.
Write what you love.
If you're a writer, chances are you're a reader. And if you're a reader, chances are there are certain themes you'll find recurring again and again in those novels you've read until the spines are cracked and the pages are dog-eared and there are unidentifiable stains on the covers and the edges from carting them everywhere while you're reading them for the forty-second time.
I'll go further, and say there's a good chance these certain themes you love are also present in your favorite movies or television shows. Themes that move you, fascinate you, make you laugh hysterically or weep uncontrollably when they're executed well.
Now, many writers discover a problem when they contemplate these themes they love: they've been done before. Obviously, since you've ran across them in so many stories. You conclude that they must have been done to death, and nothing you write on these themes can have any possible chance of success.
This is unequivocably not true.
You are the only one capable of writing the themes you love with your own unique voice, and your own opinions and life experiences coloring the story. Only your characters can handle these themes in the special way you see them and relate to them. Everything has been done -- but you have not done everything.
People fascinate me. This may seem like a very broad theme, but I've recently connected a few dots and realized there is a specific idea that's "been done" that I absolutely love: non-human entities that have suddenly become human, and get to experience all the pain and joy that comes with humanity for the first time, with a clean slate.
I can't seem to recall any books that use this theme (though I'm sure I've read several) - but I know stories. Joe Black. Short Circuit. At least two episodes of Star Trek. The idea of 'becoming' human excites and energizes the writer in me.
So I'm giving this theme some wings (HA - if only you knew!) and letting it fly. And for the first time in far too long, I'm excited about my work. Despite knowing this particular idea has been done, and these certain non-human entities have been used again and again, I'm writing yet another story. And I love it.
I'm writing what I love. Are you?