I have probably the same problem as you do. My kindle contains over 200 books that I started to read, but never finished. I've tried things like GTD, Pomodoro Technique, but it always fails for me, because I don't have enough discipline to keep doing it long term.
However I found out one thing that does work for me, at least for short term planning. And that's pen and paper.
Take a blank piece of paper, preferably something like blank A4 from your printer, and write your mind out. Make a list of all the things you'd like to do, explore or think about. If one paper isn't enough, take another one. You don't have to be organized, just get all the thoughts out of your head, so you can get rid of the feeling of this is too important, I don't want to forget it.
Once you write all the ideas down, it's much easier to organize them. Pick the ones that are actually important and take another paper and analyze them. Usually you will have loads of ideas that are kind of long term, you want to explore them, but you don't have the time to do them right now. Take those and put them in a folder.
You can then put it in a kind of inspiration folder with all your ideas. Whenever you get bored, take all those papers out and browse through them.
Over the years, I've collected hundreds of pages of notes from lectures, presentations, conferences, or just link to interesting websites or random stuff from a book. Every time I browse through them, it gives me loads of inspiration and motivation to just do something right now.