One thing I think I've misunderstood about "Getting Things Done" is the expectation that it asks for uni-stream task management. That may be something that the official materials demand, and that may be accurate to the system as it is practiced, but I don't really believe it's necessary to the essentials of GTD.
GTD must have reference to a "uni-stream" in relation to time and that's basically it. Everything must all come out of the same extension of lifetime that's available to you.
To my undrstanding "Getting Things Done" transforms problems into a request for one of these 3 inner resources:
1. Choice - which is no more than working your way through the decision tree
2. Courage - which is no more or less than engaging at any moment with the present task
3. Memory - which is no more than writing things down and reading them later
I think the version of GTD that I'd really love would be Tao instead of Zen.
I'm not a samurai with an elegant and seamless integration of purpose and energy.
I'm a mossy rock disintegrating under a waterfall and my spontaneous inconsistency is the authentic source of my mossy genius.