One thing that distinguishes writers from non-writers is that they're the people who write the most. A lot of people might wish to write and forget to write and then wonder why they haven't written.
Writing requires writing.
I don't know what it is. There's no single key. There are many people of very different dispositions and characters and orientations and temperaments who end up being able to produce excellent prose. And in it there's a chess master who's teaching another master to pay attention, and what he means by attention is think, not that you're concentrating, but that if you make a mistake a catastrophe will happen. The world will literally fall apart.