A diary should be used as an inbox that could be sources of fleeting notes like andy matuschak’s daily working log. A diary entry is still a fleeting note but more primitive by vitue of the fact that individual fleeting notes could be extracted from one.
However, I wonder if it captures something more than fleeting thoughts. For one, a diary can be analyzed and used as a source of details about my life. They are helpful to my biographer. But could they be helpful to me too?
Some people do. ralph waldo emerson, henry david thoreau, austin kleon, and David Sedaris use their journals as the main source of publishable artifacts—articles, books, or lectures. They treat them not just as sources for possible evergreens. They use exact phrases and sentences from their journal entries in publishable artifacts. They use them as prompts for writing.
But I do the same. I transfer exact phrases and sentences into my permanent notes. The process of writing fleeting notes out of journal entries simple cuts on the noise that is in a single diary entry. When you write using a diary entry, you will have to go through the entire entry and find what has the best quality. Well, by writing permanent notes out of diary entries initially, you have already done this.
So I don’t think creating an index and maintaining that by creating more indexes of indexes is a good use of one’s time. What I think could be more useful is going back to entire journals, rereading entries and writing reflections about patterns in the journaler’s thinking or the evolution of his thought like what laura dassow walls did in her excellent biography of Thoreau. But that is the work of a biographer, and that takes a lot of time.
Personally, I would rather see these patterns through individual notes in my zettelkasten.
Another reason why indexing diaries is less efficient than using permanent notes is that, when I follow an index entry, what I see is a diary entry with jumbled words and thoughts. There is no clear association between the index entry and its contents. What’s there is a murky association. Prefer clear associations.
Update
I now do indexing. It has helped me search for stuff.