You may be wondering, at this stage in your career, what kind of writing suits you best. Are you a novelist or is the short story more your form? If it's novels all day long, do you tend to find a situation and characters that lend themselves to a series, or do you prefer isolated works? (Here's a tip from the fantasy-reading community: series sell - people invest in the characters, and are disappointed if they only get one book’s worth of them. This is why publishers love a series - it's not simple laziness or the desire to have a built-in revenue stream - it is a response to how people are.)
If you suit the shorter form, how long should your idea be? Flash fiction won't earn you much, but there are plenty of competitions and the investment of time is low (although the fewer words in your piece, the more attention you will have to pay to each one). Short stories can be anything from 1500 words to twenty times that. You probably have the story before you know of the competition, and it may need to be pruned or padded to meet the word length.
Novellas, basically half-novels (30-60,000 words), are hard to place. A short novel (under 70,000) is also difficult to sell, except to Mills and Boon. A novel is generally 60-100,000 words. Over 100,000 and it becomes more expensive to bind, if you're going to go down that hipster route and have an actual product.
In summary, writing is like being a runner. There will be a distance that naturally suits what you do. Remember, though, that you can always lose 10% of your work in an edit without doing it any harm, and you’re likely to do it quite the opposite.
Speaking of Mills and Boon, let’s talk genre. You might think genre deserves a post in its own right, but it is merely an artificial way of categorising creative output so as to sell it. For a while I tried to write romantic fiction. After all, my stories did have love at their root. I joined the Romantic Novelists' Association, went to their workshops and conferences. But my characters were too spiky, too wounded. It may be that romance will suit you - if you find that love is at the heart of your tale, I would strongly advise you to join this organisation and give it a try. It's a huge market.
I found what I was by going back to my roots, to the child who glutted on fantasy and binge-read Rosemary Sutcliff. The word 'literary' is a catch-all. I'd prefer to say I write 'speculative fiction.' Which is not confined to sci-fi, but which starts with 'what if ...'
There will be subjects, or plotlines, that attract you. These will drive what genre you decide to shoehorn yourself into. First, write your work. Then, label it. As long as the label is close enough, no one will complain. Use two labels if you like. You may have invented something that is gold-dust to an agent: a novel that has created its own category.
Above all, don't try to write what readers want. No-one really knows what readers want. Not even readers know what they want. Just write what you love, with as much passion as you can, in the amount of detail that works for you, and then, when it's done, you can give it a name.