Over the years, I’ve downloaded a lot of old emails to my laptop, which I saved as .eml files and then converted to .docx, .odt, and .txt files (mostly the last two).

The unfortunate habit of almost everyone (including myself, but no longer!) of quoting the original message as part of an email exchange has left me with text file(s) full of repeated sentences and paragraphs. What I’ve tended to do is to dump all the text from a one on one correspondence into a single file (“Dad-Erinaceus Complete Correspondence.odt,” for example) and then try cleaning it up and re-ordering the messages by date.

Apart from the emails, I have I guess what you’d call a “journal” which is a very long .odt file that runs to about 300 pages or so. Much of this has the same sentences and paragraphs over and over again, but sometimes with slight variations that I would like to keep. So far, in either .odt or .txt files, I’ve started by searching for the first sentence, deleting subsequent appearances of it, and then going on to the next sentence, and so forth. Very time consuming! Is there a faster (and safe) way to do this?

There is quite possibly a very simple solution to this that I haven’t thought of, but I’d be much obliged for any suggestions.