tldr: Though I've been writing fiction for a long time, I have no real training or experience. I've put a lot of thought into a fantasy novel idea (we'll call it the Hail Mary) and am excited to write it. Should I focus on other projects to hone my writing first, before going for the Hail Mary?
I started writing when I was young, I think I started my first novel when I was 11 and wrote through my teenage years. I was never one for outlining, and I didn't finish many of the novels I started, but I wrote pieces of ~15 novels between the ages of 11 and 17. The majority of these novels were in the fantasy genre.
However, I don't have any professional writing experience. I read a ton (of course) and I've read articles online on how to write. I took two writing classes in college, but they were academic, style-type classes. (I'm an engineer, these classes were about that kind of technical writing.)
I can tell that my writing improves when I am writing more. So, since I haven't been writing as much in the past few years, I feel rusty. I've recently put a lot of time into developing a fantasy world and the plot to a story that is a culmination of the best ideas I've had in years. To the point where I've outlined it chapter by chapter-- something I rarely do-- and it's exciting and interesting (to me) the whole way through.
Should I dive in on starting to write this? Or, since this is my "Golden Goose" should I develop my writing style and practice before I start? I've been using five-minute prompts to write short stories within this world. Is this a good way to practice, or should I be focusing more on writing the actual novel and editing the hell out of it? Would it be better to start and finish an actual (short) novel for practice? (I have plenty of ideas, just not many as "good" as my Golden Goose.)
Any advice would be appreciated, I'm in uncharted territory. I've never wanted a piece of mine to come out better than this one! Thanks in advance :)