In the martial arts, if you get stuck you go back to basics. The simpler techniques contain all the components in the advanced techniques, but usually in a less complex environment. If a particular move in a particular kata is giving you trouble, you can work on that move in isolation in one of the more basic kata.
In the performing and visual arts, there are fundamental exercises that you do in order to both warm up and teach your body the desired movements: fingering exercises for pianists, voice exercises for singers and actors, basic studies for painters and sculptors. If you don't practice these regularly, it becomes very difficult to improve beyond a certain point.
I think the basic disciplines of GTD are in much the same category. I know when I'm feeling overwhelmed it's very helpful to go back to the workflow diagram and force myself to stop and really think about each item in my inbox, or to methodically work through one of my context lists. Under the same circumstances, it can also be very helpful to add "fun" stuff to the lists: things that I normally do without prompting but don't feel I have time for when I'm feeling swamped. (Which could be anything from playing with the cats or taking an ice cream break to escaping to a park for the afternoon.)
I was just searching through the forums for the word Martial and came across this Post. Thank you Katherine this is exactly what I needed for Work, GTD, and martial arts. I have been really frustrated at work lately and you are right. I need to go back to the basics.