Personally, that's note taking.

I've been using Evernote quite heavily over the last few years. Originally as a replacement for Google Keep and Pocket/SaveForLater. Lots of notebooks and an organised tagging system seem to be the key for me.

I use it for jotting random thoughts on the train, as well as a variety of journalling purposes (everything from tracking training courses watched to having little retros after cooking something - so I can memo tweaks to make next time).
I also use it to help me internalise keyboard shortcuts of the things I use the most of the time. Random memories from childhood as they occur to collate and print, in case my memory isn't so great when I get much older.

More relevant to the question, I use tags like "#StartDoingThis" in a variety of contexts, which are different notebooks. Could be related to programming, household stuff, music, health - anything really. I set an alarm at the weekend to review the stuff that received that tag during the previous week.

Also tried using Evernote for a 'Return on the day' sort of note, where I jot down a few worthwhile things I'd like to have done by the end of the day to have felt there was some sort of gain.

Taking a quick glance, I also have notebooks for things I tried differently that made a noticeable difference, old habits that I should bring back that were better, resources I've noticed that have been overlooked (that book on Kindle, a saved training video), technical videos I saw on YouTube that made an impression. A list of positive things as they happen, to reflect on later and feel happy about... Activities that made me feel particularly enthusiastic or engaged, so I can dig that out and try the same sort of thing again if stuck in a rut.

I'm really into playing instruments and home recording, so if I hear a piece of audio I like, I record a ten second snippet of it, and put it in a notebook with tags detailing what I liked about it (arrangement, production, effects, bass part, groove, riff, solo, harmonies, technique) so that I can dial in on one particular tag and listen to all the clips if I need some inspiration.

All sorts of things, really. It's good to periodically drill down on a tag or notebook and see there's some worthwhile content or good insight there.

During my working day, I use a program called Marxico that's a great Markdown editor that stores notes within Evernote organised by notebook and one or more tags. I like it because it's based on the Ace editor, so the Vim keymap works really well. Writing well structured documents in Markdown is really easy now. When I start a new Scrum or Kanban story, I have a note associated with it. I first define sections for things like 'objective', 'reference notes', 'problems' and 'tasks', and use bullet points obsessively to structure hierarchies. I used to try and do this with mindmaps, but it's much quicker with Markdown and bullet points - especially when you're tearing around with Vim expressions. That task sheet really dictates how I work on a story, and it's incredibly quick to take quick screenshots and paste them into various levels of the document as and when needed. When the story's over, it will be automatically synced to Evernote for future searching. Really helps me to keep focussed on important details.

Will have to keep looking at some way of automatically backing it up locally in a neutral format, though, to offset the vendor lock-in.