Writing fiction is like building a bridge across a chasm, of unknow(able)n depth, using nothing but bits of material of dubious quality, some of which have been eaten by termites, never knowing if there is even another side to the chasm, or if the materials you've got are just going to give in half way. And sometimes you don't know if you've made it to the other side or fallen through until it's published and even then you can read it and realise that you didn't and it's out there for all the world to see*. I'd even posit that this is actually most times. But building rickety bridges is a hell of a lot of scary fun.
* well you wish it was, even when you hate it, part of you wishes it was.