There are three keys to keep the creativity flowing, the boys in the basement active, and the muse at the quill. First is to read, read, and read. Second is to learn as much as you can. Third is to write even when it sucks.
Reading in the genre that you write in is important. You learn new tricks of the genre. You keep up on what is trending. You understand the themes and structure of the genre. It is also important to read outside of your writing genre. By reading outside your genre it flexes your creative muscle. New ideas pop into your mind because it combines with the ideas you already have going. It adds a special twist in your novel. I’m not suggesting you combine genres, but you could. What I’m saying is that different genres do certain things better than others and you can learn to be better by reading outside the lines.
Continue to learn about structure, characters, dialogue, and every other area of writing. Strive to improve over your career as a writer. I have found that I need to keep a notebook near at hand when reading about the ins and outs of writing. Ideas for new stories and current ones spring into my mind as I discover new ways to look at things whether it is scenes or sentences.
Write as often as you can. For some this is every day. For others it is every other day. Whatever it is for you, keep doing it and do it regularly. It might be total crap that you are writing, if it’s a first draft it is total crap, but keep doing it. You will get better. However, if you stop you will not get better. Quitting is the end of the line. The chance of success drops to zero. Write all kinds of things. Don’t box yourself into one type of story. Write poetry, short story, novels, non-fiction, fiction, and in any genre that calls to you. I find it easier to have two projects going at the same time, that way, if I get sick of one I can still be productive on the other.
The balance between the three keys ebbs and flows, depending on where you are in your journey. Stagnation and loss of creativity is a sign that you have misplaced one of your keys.