1.Nothing is as Bad or Good as You First Thought
Rereading a first draft of a novel (or a second or third draft for that matter) is an adventure. I discover brilliant scenes I'd forgotten, unearth little threads of subplot that I don't remember weaving, find little gems of dialogue that make me all happy inside.
I also find a fair number of turds: descriptions that are not as clever as I thought they were when I first put them down on paper, plot holes I can throw a cat through, characters who seem cut from cardboard. Some of it is ugly. And some of it beautiful.
The point is, early drafts are allowed to be a mess, but chances are they are not as bad as you first thought when you typed "The End". That's what revising and editing are for - making the bad better and the good really good.
2. Trust Your Gut
Revisions are hard. There's that constant feeling of "But what if I make it worse?" There's the nagging suspicion that you won't have improved while writing the first draft and the second one will be more of the same drivel. There's the fear that if you try and change things you'll lose the thread of what you loved about the story in the first place.
But beneath all that is a sense of what needs to be fixed. It's the voice that says "That character doesn't serve a purpose here, get rid of her." It's the tingle of intuition that says that your MC's flaws are more interesting than her strengths. It's the whisper that tells you "That person has to die if the danger is real." This is your gut, the muscley side of your subconscious. It is always right.
3. Take Small Bites
Novels are hard to rewrite/revise/edit because they are so much longer than a short story. (Duh, right?) Take small bites, work on it consistently, and don't give up. Much like writing a first draft the middle will probably seem like The Middle from Hades or The Second Act That Ate Chicago. The difference here is that you already know how things end. You can stop to fiddle with an ornery scene that sets up the final conflict. You can take the time to develop that subplot with the romantic secondary character.
Where writing the first draft was a necessary push to get the whole story out on paper, the second (or eighth) draft is about fine tuning all the moving parts. Take it one step at a time. If it takes a week to revise one chapter and only five minutes to revise the next... that's okay. Mashed potatoes take less effort to chew than ciabatta.
4. Set Goals and Celebrate Accomplishments
Aim for a certain number of pages edited/revised at each session. Be honest about what you can accomplish, but give yourself a little challenge too. Just like with word count goals you may miss the mark sometimes. And sometimes you'll go way beyond what you intended to do. But without a goal it's easy to fall into the trap of moving commas around. Really easy.
Goals help you keep in mind that this is not the only chapter that needs work. And don't forget to celebrate when you make progress. That may mean an extra piece of shortbread at tea time or taking the evening off to something fun (or to veg). Whatever you choose to do, don't forget to recognize that you are making progress. Even if it's slower than you'd hoped.