My bandaid may not fit your wound, but here it is all the same.
When I'm editing, I break it down into sections to make it more palatable for me and my ADHD-having muse.
First I work on the plot holes and place notes where needs to be beefed up, and where needs to be trimmed.
Then I go in and start trimming the fat. Unneeded scenes marked on the previous pass-through are cut and placed in a separate document (they sometimes come in handy later, so I don't delete).
With this done, I look at my target wordcount, and I allot words to parts that need to be beefed up. Then it's down into beefing up those scenes.
When I'm done with that bit, I go over the whole WIP (Work In Progress) for new plotholes and rough patches and I start marking those (this is purely a read through with leaving notes). Parts that absolutely HAVE to make it into the final draft are highlighted one colour (I prefer green), parts that are a bit rough are highlighted another (I prefer yellow), and parts that are apt to be cut are highlight yet another (I prefer red).
Then I open a new document and I start writing it all again. The green parts of every scene are put in. The yellows are reworded and smoothed out. And the reds are only used if I fall short of an allotted wordcount (but heavily reworked so it no longer makes me cringe).
Once I'm done with this phase, I go for a complete read-through again. If I'm happy with it, I wrap it in a nice little bow, and I send it to my beta readers. If I'm not, I go back to the first phase and start tearing it apart again.
After I get feedback on a chapter-by-chapter basis from my betas, I take their critiques into account and figure out what needs to change on a scene by scene basis (while making meticulous notes what this will affect down the road).
Do this a few times, and I feel confident my work isn't going to make me cringe when I hand it to a cold-beta (who I keep separate from my alpha readers and the betas that have already read the previous drafts).
So how do you stay motivated through it all? Well. What I do is remind myself of one simple fact:
I am a writer. If not this, then what?