What's the most torturous part of writing?

Grace wrote awhile ago that first drafts were "the most torturous part" of writing for her, and explained why and how she broke through the barrier.

They definitely are for me, too: revising I can brute through, whether I'm tired, whether I have an idea or not--but that first draft! In the past, anyway, I haven't handled first drafts as well as Grace does. I LOVE writing first drafts while I'm inspired; but there always comes a point when I am not, and when that happens, I babble. I just write nervously, the way I might once have talked nervously at a party (I've since learned to be quiet in those circumstances).

But when it comes to writing, I babble, then get very discouraged by how awful what I've written is, so discouraged that I sometimes stop. This is the worst thing to do! It's better to just sit there, not writing, until I think of something true to say, something I want to say, something I find interesting. And if nothing comes up: just sit -- and eventually, something that moves the story along again will come to me....it doesn't have to be great, just something with some life (energy? sincerity?) to it -- something that's truly part of the story, that is. An irrelevant scene or detail -- no matter how charming -- doesn't count. And it definitely doesn't have to be well-written --writing (including details to bring the scene to life for the reader the way it is for me) I can fix later, too. But it has to be something *I* find interesting and believable-- something alive to me that keeps the story moving.

A side note -- I'm having a hard time defining exactly what I mean by "alive" or "sincere" -- it's that quality in a book that makes it feel real while you're reading it....that makes you almost forget that you're reading words on a page and feel "in" the world of the book. Its opposite is contrived--when you can see what the writer is trying to do or force; and a lot of modern writing feels contrived to me. MINE does, when I'm babbling and forcing! And that's the hard thing about first drafts -- if the book is ever going to be any good, some part of it has to just COME. It can be worked on and fixed later, but if there isn't some spark of this inspiration or whatever it is, the book will never be any good.

I think one reason writing every day, at the same time, is helpful is that after awhile your mind learns that you're going to be sitting there waiting, so it might as well come up with something. If it doesn't, it's not going to get to go to the beach or have a little snack: it's going to be just sitting there, facing the page (not email, not a Web site, not cute dresses on ebay, the page that needs to move the characters along.

I really hope to be able to report at some future point that I did this and it worked....but in the meantime: What's the most torturous part of writing for you?