There is this video from Stjepan Tomic he has a 5 to 6 hour 3 stage process for learning from his mistakes.
Personally I don't have anywhere near that much time to spend analyzing games, but I think the three different kinds of analysis he mentions: self analysis, reviewing GM games, reviewing the engine, are useful.
What is the next target that you are aiming for? Mine is to reach 1200 by end of June.
One of my next goals is to move toward purely self-analysis of my games rather than flicking through the post-match engine...
I know I can go through and start annotating my losses on here - look at where I gave up a piece, lost an exchange, made a blunder etc. and then reverse engineer that position to see how I ended up where I did and make a note of what I did wrong or what my opponent did well. I'm guessing this is the main idea behind self analysis (as well as looking for missed strategies).

What I'm not sure of is whether annotating and analysing a game is the main point and I just slowly start to learn more patterns from doing it often or if people take a more systematic approach? Do people keep notes or any other systematic approach when doing this? Is that just overthinking it at this point?
I mainly play daily at the moment and had an enjoyable surge up to 1000, but I feel like to push forward from here is a much bigger challenge, so as well as picking up some books to read I'm also thinking of the next stage of learning as being a different challenge altogether.
Visual representation of me hitting 1000+