I've been coming up and using various GTD systems for a better part of the last two decades. I'd be slipping in and out of different setups, tools, solutions, systems... Some would stick for years, the others I'd abandon pretty quickly.
All of them worked for me to a degree, and were very helpful in keeping me organised and efficient, but never did I find a perfect setup that I'd be perfectly comfortable and happy with.
I guess the most useful thing I learned from all these years and years of trying to get a system in place and trying to get organised is to be perfectly comfortable with changing the systems as I go along. Keep experimenting. Keep what works for you, discard what doesn't.
For a long time I've been using a combination of a Trello based implementation of a GTD-gone-wild kind of a todo list (with the centerpiece being week-by-week daily todos) and an Evernote based journal that I kept surprisingly consistently almost every day for years.
A few months ago, I got in one of those overwhelmingly busy crises, which made me drop the journal. Rather than daily, I'd do it occasionally. To an extent it was a relief, and I rationalised the hiatus by thinking in terms of the benefit from the valuable extra time that I could spend on other work, but I quickly realised that I lost an important information repository I could comfortably and consistently rely on.
And then I stumbled upon Roam Research (RR). The experience was so great that I started keeping a daily journal again. Went from 'nah, I'm not writing shit' mode to an almost obsessive 'gotta record everything' in an instant. And I'm actually enjoying it.
I've ditched Evernote (I still have all my old data there), and I did not think twice, cause I got used to evolving my system without looking back if I find something that i feel works better.
At the moment I'm still using Trello for tasks, but the todos are so easy and natural to do in RR that I'm increasingly using it for my tasks, and finding that I am having to open Trello less and less.
RR is so powerful and flexible and natural and easy, that I am genuinely excited about a prospect of evolving my next system on it. I have a sense this one will stick for a while.
There's a very helpful article on Medium, written by a guy that's quite serious about getting the most out of RR. I'll try to find it and link it below.
If someone reading this feels the same and would like to hack together something like that, let me know and we could try it together.