I'm currently in the middle of a major rewrite of my first novel. I call it a major rewrite because I am retyping the text -- it's not just an edit where I fiddle with the language or add a bit more setting here or sharpen an image there. I talk to my students about the importance of re-vision, as opposed to just revision, the act of re-seeing the novel, reimagining it.
The way I approach this is to have a quick reread over what I've already written, and then think about what I was trying to achieve in that scene, and whether the scene is as effective as it can be. Then I have to put the old scene aside and have another go at it, without looking at what I've written. I can't look over it again, or I find I'm just copying the same sentences, perhaps with a few minor changes. Totally pointless.
It's easy to re-vision a scene that feels flabby or that isn't working as hard as it can. It's the scenes I'm really happy with that I find the hardest, because there's always that temptation to go with what's already down. But the rewritten scenes are invariably stronger than the original, so I have to resist that urge. When I'm finished, I can always compare the two and take back anything that seems absolutely fabulous that has now been omitted. Occasionally, I do take a sentence or two, but often these are moved to someplace new.
The draft is chugging along nicely, and it's the first draft I've been really happy with, so now I just have to make sure I keep my bum on my seat and keep at it.