Personal organization/management is something I've always found appealing. I think it's because I like collecting statistics, and getting information about myself is much more conveniently done than other sources. Developing organizational systems is just fun as well. Here I've gone over past and current methods I use for dealing with various items.
Diary and PKM Systems
My diary has taken a few different forms over time. I used a physical notebook when I first started making regular entries. Two years ago, I switched to digital but just recently have gone back again. I didn't have a strong reason for switching back but just felt like writing more physically. My diary entries consist mostly of the rambly sort of stuff you'll find in my art journal. While I was doing digital entries though, I learned about personal knowledge management software and tried out both Logseq and Obsidian. I used Obsidian for my diary entries for a few months and moved my loose digital notes into it, which I still use for that information. I keep a to do list (which I pretty much ignore), reading list, and write down ideas I get for paintings, writing, or whatever else. I also switch between interests a lot so I write down the date and what topics I've been thinking about recently.
I realized that this site is also a form of personal organization. Corralling my ideas into a more presentable manner is definitely helping me straighten out some concepts in my head. Considering how to structure this site has also been helpful.
Tags, Not Folders
I've been feeling the limitations of folder schemes for some time now. The issue is a lot of the time there's two or more broad categories I would like to file something under, but the categories might have nothing to do with each other, so it doesn't make sense to nest one in the other. The clear solution here is to allow files to be placed in two folders at once, or be given tags, in other words.
My collection of digital images is definitely in the worst situation at the moment. I have about 23,000, saved over the course of about 3 years. A large amount of it is art, but there's also many photographs of architecture, portraits, clothing, interesting lighting, etc. The main reason I have so many is to use them as reference for paintings. My rule for a while has been whenever I come across an interesting image online, to save it or occasionally take screenshots of a video frame. With the current way things are though finding specific pictures can be a real pain. The issue is that they are largely untagged and scattered across many folder classification schemes made in previous attempts at systematizing them. I've started to tag them using DigiKam but I've hardly made a dent.
Ebooks and PDFs
My situation with those is much better, mostly because there are far fewer of them. I use Calibre to tag and otherwise manage the files. It has a feature to create a separate tab (they call it a 'virtual library') that can update the collection of books inside of it based on the specifications you set. I use it very simply to have a 'reading' tab, which just displays the books with the tag I use to note I am currently reading it.
I do have some stuff locally managed with MusicBee, but I am not that interested in music generally and don't listen to much. I pretty much only use YouTube or Spotify when I do though. I have BlackPlayer on my phone which has most of the same local files on my computer. I use it sometimes when I'm outside and away from my computer. Which is to say, it doesn't see much use.
I use Goodreads, MAL, and Rate Your Music. The funny thing with RYM is that I only use it for movies because I don't listen to music much. I generally don't give ratings to things because I find them hard to quantify.
Time Tracking Software
I use the free version of ManicTime to track what I spend my time doing on my computer. A fun fact is that I have more time spent playing League of Legends than in Photoshop (which is the only painting software I use) over the last 3.5 years; 1995 hours versus 1825 hours. Sadly, despite my large time investment I don't think I've improved all that much, odd certainly worsened by the fact I only play aram nowadays. To further digress, my peak rank was failing platinum promotions in season 2021 as a support pyke one trick but I haven't played much competitive since. I swapped to mid last season and played around 80 games. I was only stopped from demoting out of gold entirely by the 0lp shield. Definitely some strong anecdotal evidence of support being the easiest role... But back on track, my most used application by far is my web browser with 4485 hours. Geez.
I still don't have a dedicated drive for backups. At this point I've been meaning to get one for years...