I’m listening to Making it All Work, same author of Getting Things Done (GTD). One key principle is to ‘write idea/ to-do down when it arises if it’ll take more than 2 minutes. If it’s under 2 minutes, do it immediately’.
Many books emphasize ‘taking action’, e.g. 5 Second Rule (which proves very effective for me to get up after alarm clock sets off, no snoozing or nagging) or as my mom says ‘怕麻煩惹的麻煩越大’ (avoidance or laziness will get us into bigger trouble).
To me, writing it down, choosing what’s most important to do first, and sticking to it (regardless how easy or fast the other tasks may be) will bring the best of ‘Productivity’ and ‘Peace of Mind’.