5 Horizons
If you're thinking of next actions you're only in the lowest horizon. The GTD methodology is to get the next actions under control so that we can think about our life from the higher horizons with the focus that they deserve.
Looking down, our life purposes shape our goals; our goals allow us to choose which areas of responsibility to accept; to fulfill the duties of an area of responsibility you must finish projects; projects are comprised of actions.
The GTD methodology is a bottom up methodology. You get actions under control so you can properly think about projects. You get projects under control so that you can properly think about areas of responsibility. You get areas of responsibility under control so that you can properly think about your goals. You get your goals under control so that you can properly think about why you are here.
Jake