In one of the Writing Excuses episodes, Brandon Sanderson said (and cited others who said), that one of the biggest advantages they had as beginning writers was that they had no idea how bad they were.
I was, and still am, so jealous of that. I realized how bad I was when I was about sixteen. I submitted something to the Reader's Digest and it was, of course, rejected. As I considered what I'd written I thought, "Wow. I suck." And that knowledge stayed has stayed with me for fifteen years. It's part of the reason I never took my desire to write seriously.
Jessica Day George has said that during first drafts, she's like a toddler on a sugar high. I envy that, too. First drafts are agony for me. With every word, I'm shooting myself corrections. "POV slip. Not enough conflict. Action doesn't rise high enough. Redundant descriptions. Wrong character carries most of the action. Cliched phrase." And all the time I'm wondering to myself, "Do I go back and correct these things? Do I make marginal notes? Do I fix this section even though I suspect that doing so may require a massive rewrite of several chapters or even changing the main character?"
I try to take the advice of authors whom I admire, and the almost universal advice seems to be no, don't revise. Finish the draft. It may not be as broken as you realize. It may be much more broken than you realize. Either way, you need to view it in its entirety before you can really know what to fix and, more importantly, how to fix it.
What keeps me going, aside from the grim determination of imagining I'm smothering a jar full of mice, is trying to drop myself into the scene, to forget about the words and just see the characters bursting into motion, to feel the things they're feeling. (I suspect that this makes my face look really weird and MPDish when I write.)
I wonder if it's worth it. I wonder if I'll be glad I did this in the end.