Here's a secret: fictive text doesn't necessarily flow easily. Most of the time it's more like cutting a highway through a mountain. You just have to keep working with your pick, chipping away at the rock, making slow progress.
I did not know at first that it would be a series; I discovered after the first novel that I had more to say about it, so I did another. And another, and then the readers demanded yet more.
Normally I work out a general summary of what I mean to do, then start writing, and the details can be different from my anticipation. So there is considerable flow, but always within channels.
When I started writing this, I found that I simply couldn't take fantasy seriously, so it became humorous, and continued from there.
Keep writing, because not only does practice improve skill, it gives you more chances to score on the market. I did that for eight years before making my first sale.
Have a working spouse, because you won't earn a living from writing - not at first, if ever. My wife worked for years to support us.
It would be easier to write a novel without reader input, but I feel the fiction is richer for it.
I never do a full outline, and if I did, I would not feel bound to it, because the view from inside a scene can be different from the view outside it. But neither do I just start writing and see what happens; I am far more disciplined than that.