Vimwiki [1] is probably also worth a mention because it has a neat diary feature as well. Jrnl appears to have more diary specific features, but Vimwiki also worked well so far for my (probably rather basic) needs.
It’s a text file where I’ve copy and pasted paragraphs and comments I’ve found interesting from books and online, and a few of my own thoughts.
Each entry is preceded by the date the entry was made, and followed by a reference to the source.
Because I’ve used some of the material multiple times I’m vaguely aware of the overall structure, and I use it as a bit of a knowledge-base.
As an example I’ll probably pop this comment in there later, so some of the materiel is mundane. Some of it seemed profound in the context of my life at the time, but might make less sense years later out of context.
I’ve only ever deleted a handful of entries in that 17 years.
I guess parts of it are a bit like a diary too, but I’ve never been very good at intentionally keeping a diary.
I started this file 17 years ago!
This is enough to fill three average sized novels!
One day... I might have a go at weaving a narrative through it.