You've got your draft and now you come to edit it. The problem is that you've been looking at the same words over and over for so long that it's difficult to see them clearly any more.
How do you put some distance between you and your draft? Time is the best distance but you may not have it. A week in a remote cottage would certainly help focus your mind but that's not a realistic option for everyone most of the time. There are some tricks we can employ.
Read your work aloud to your furniture or your pets and imagine they're the audience at a cool, indy bookshop reading or in the marquee at a literary festival. Listen for the dud notes, the places where the energy seems to flatten. Notice the rhythm and pacing. Notice where the dialogue sounds clunky or isn't doing the work it needs to do. Listen for the great bits too, enjoy and be proud of them.
Try going for a walk first or doing some activity that's completely different from writing. Try taking your editing somewhere that isn't the room where you usually write. It can be good not to have your own stuff around you, or the stuff that was around you while you were writing. A cafe or library you don't usually go to can be just right, maybe in another town, maybe a place where you don't know anyone. An out-of-rush-hour train journey can be great for separating you from your familiar, everyday things and giving you new perspectives.
Try things out and see what works for you. Print out your work in a new font if that gives you the sense of slight detachment you need.
When it comes to plunging the knife in, you can usually cut much more than you think you can. You should certainly try. This is not necessarily the time to be kind to yourself. It's the time to be honest. There's often something that your editing brain knows isn't quite right but your writing brain declines to acknowledge so the offending section or element stays as it is and the work never quite takes off. You might need to rewrite your work from a different point of view or in another tense. You might need to cut the first thirty pages or start the whole thing at a different point in time. If you know it's right but you just can't face doing it, do it. Try it.
Cutting with precision at sentence level can add life and energy to tired prose.
Be sharp, be fearless and enjoy the pleasure of cutting out the stuff you know you don't really need.
Don't be business-like and competent when editing a draft but be bold, brutal and take some risks. It always pays off. Editing can be the most thrilling part of all.