Having a monkey mind is what we Buddhists might call believing our thoughts. Not a good idea for the most part. When we are revising we must quiet the monkey who will be chattering to us endlessly about how crappy our manuscript is and how we should just forget it.
How do we quiet out monkey mind? Well, first of all don't get engaged with it. Don't argue with monkeys - it just doesn't work. Say you hear your monkey mind says something like "this stupid novel is no good and who needs another book anyhow and your mother was right, you should have been a librarian. You certainly shouldn't bother with such nonsense as writing or any creative thing. Just a waste of time." (Whew! I'm way too good at bringing up a monkey mind train of thoughts) You might try arguing back "Well now I'm not sure - I think the world could use a good novel about love in Northern Climates and blah blah blah." If you do your monkey mind will go "pftttttt!" at you. Instead try something firm and decisive "Yes, you might be right but I'm in charge and we're working on this revision." And then smile at the poor little thing and get back to work. You won't believe how quick that monkey will fold her tents and slip away.
Some other ways to quiet our monkey mind are to keep it busy doing other things. When it starts in on you it is because that part of you is scared so distract it. I might say (or think, because sometimes I'm in public) "You know Monkey Mind - I have a problem for you to solve - I need to know how to get my protagonist out of Wisconsin in one piece - I'm going to work on my next chapter and I'd like you to ponder that while I do." This works and I'm not sure how nor do I care. All I care is that it works.
Also - our Monkey Mind can be diverted by making sure we get plenty of exercise, good food and lots of premium sleep so keep your body in optimum shape when you are marathoning your way through a revision. It is crucial! (every time I think or hear the word 'crucial' I think of this British show in the fifties that had a doctor who had a Scottish nurse named Janet that used to say "But Doctor - it's crucial" with her thick accent. Does anyone have the vaguest notion of what I'm on about?)