(Making things up) Writing fiction when you just know what you want to have said
Lets say you have a - gently and generosausly put - very broad, fuzzy and general idea of a story. And worse, you have a elaborate feeling and scenario of what happens once you've wrote that idea.
Having thoughts like "This is the story that defines its own genre" or "I'll hurt my readers - if I could punch them in the face through the pages, then I would. Sadly, the best option I have is to write this" and such. Or having them more frequent than "I'll feel awful when we arrive here, but it must be done", "I love X character, I don't know how and when but I've fallen in love with my own creation", "It would be fun to have X and Y happen, but for this to be a better story I must do Z" and etc etc etc. Pattern: Thinking more about having written the story and picturing its impact and ripples rather than having the kind of thoughts that persons writing have.
Not to condemn, I don't think this is "inherently" a bad thing. But its clearly... inconvenient, to say the least, if your final goal is actually writing a story.
Actually, let me rethink that. Is writing a story a "worthy" goal in and out of itself? Is it "worthier" to want to draw because you like drawing, or because you need to have something drawn? I know people that would say it doesn't matter what's worthier, in the real world art is constantly being puked by artists that cannot hold it any longer. I only consider this point because it may be usable when considering what I've said in the title: writing when you actually rather have written, because you need to get it out of your system.
I don't follow the "oh god please anybody help me I need it out please god" school of torture art, even though it seems to be very popular. Maybe as a coping mechanism of not wanting to do the act of art, but wanting to have done art? A beautification of wanting to have written instead of writing. I wouldn't know, I'm not that high level in art.
But even thinking about what you want to have written is useful when figuring out what to actually write. Pay attention.
"Its it own genre / its not defined by genre" don't try to search for a genre. Don't even think about what you're saying. Pay attention to what you want. The intention. "I don't want my art compared / I don't want to follow trends / I want to do something new / I want to make a reader actually feel something / etc etc etc".
There's a whole bunch of these that I would put into a separate category called "meta objectives" because these don't actually depend on the content nor the act of writing, but in what this is and how it was done and what its done. Do not mix with actual objectives of writing; use like salt, and they'll boost you, but focus on these and you'll kill your meal.
"I'll get rich / I'll get famous / Everyone will be surprised when reading this" And a bunch of others that involve you. Or I. The I person. Whatever conveys a reaction that reaches to you. These depend wholly on things that you have little control. But its possible. Do good marketing, cultivate public presence, practice your skills, etc etc etc. Do not mix with actual objectives of writing; this is how you get it done and what you do with it, but its not doing it.
(Btw I'm just writing to myself, so I'm telling this to myself, if you're ever thinking that writing in and out of itself is a viable way to get rich, famous, impactful, etc. Please unpack your real inner desires, as this may be a classic example of what you want is not what you need.)
"This will hurt / I love this scene / This turn of events is evil / etc etc etc" these are reactions to your own working on writing. Different than writing but useful for our case. Again, watch for intention. To do something evil, to do something fun, to do something interesting. Its more interesting to ask "what's interesting about this?" "What's so evil about this?".
I propose this kind of interrogation of your own ideas to "feather collect" what you actually want to write. Discover your own story / book / monograph / whatever feather by feather. A way to discover the way back, starting from what you want to have done to what you have to do.
I'm not sure if it works. Maybe it does. I'm making things up. It just so happens that this month is an amazing chance to figure out.