So when I'm working on a novel, I do not, under any circumstances, go back and reread what I've written until I have finished the whole thing. Too much discouragement can keep me from getting to the end. Once I get the whole thing written, then it's time to read it for the first time. And, yes, it can be painful, because, up until then, the novel is still that pristine and perfect thing that resides in my imagination. The words never quite live up to what was in my head, so that first read-through can be a slog. Rewriting, for me, becomes a process of shaping those clunky words into the best approximation of what I had in my head. There's just a lot of work to be done.
Now, that makes it sound altogether unpleasant. However, from time to time, as I read through the first draft, I find a passage, a paragraph or maybe just a sentence that turned out just the way I wanted it to. That, ladies and gentlemen, is a sublime moment, and it makes all the rest of the work worthwhile.