Engage

The fifth of GTD’s five steps: doing — choosing the next action to take from the lists, by context, time available, energy and priority, and taking it, trusting that everything not chosen is safely somewhere it will be seen again

Allen’s point is that the earlier four steps exist so that this one can be done without anxiety. The four criteria for choosing are in order: what can I do here (context), in the time I have, with the energy I have, and of those, what matters most. The threefold model — predefined work, work as it shows up, defining work — is the honest account of where a day goes.