I'm now (finally) at the stage of study where I'm going back to some of my earliest work and rewriting it. I'm still too frightened to touch some of the material that I put into an "introductory chapter" as I know that firstly I have to write the introduction last and secondly that a lot of this material may be moved into the conclusion or put elsewhere! So I'm starting with my first "proper" chapter. In theory, other than the introduction, this is the chapter that needs the most work, as I'd done the least amount of research when I wrote it. All the later chapters are shaped by what has gone before, but now I need to shape the earlier chapters to reflect what comes later. Sounds confusing? It is, a little.
I'm very grateful to Younger Me (TM) for being so organised as it took me about 10 minutes to dig out all notes pertaining to my first chapter - that is all comments on the chapter itself, rather than all the material that's gone into it. Now I'm starting to work through the comments and see what changes I need to make. I've found that the start of the chapter is unclear so I've started rewriting it.
Now I'm not hugely confident in my own writing skills at times, and there are moments when I feel that I have to rewrite a paragraph, or a series of paragrahs to such an extent that all the original text is deleted. This is sometimes hard to do - and not just because my supervisor has drilled into me the importance of keeping copies of drafts in case I decide I prefer something I did earlier and then can't find it(!) - in case I'm ditching something that I might turn out to need later. I find that the best technique for this is to cut the text in question and paste it into a new document. Give it a sensible name and file it somewhere obvious.
That means I can write the new text with a clear conscience and in a month or so, when I come to look at the new document again (in this case, I've saved it as a possible ending to the introductory chapter, rather than the beginning of the current first chapter), then I will have the perspective to agree with my Not Much Younger Self (TM) and delete it without regrets or insert it elsewhere.
In other words, to help me delete my own work, I pretend to myself that I'm not really deleting it.
Which actually is not a bad technique, because it might be useful to me later on. Younger Self (TM) has proved that many times over.
... and now I'm going to stop talking about writing and editing and go back to doing it!