Productivity is a measure of your output divided by your input.
Output is measured by the importance of the accomplishment to your goals. A person who outputs lots of unimportant stuff is still unproductive. Importance, not sheer volume, is how output ought to be measured.
Input is measured by the time, energy and attention you have available. Sometimes this translates to speed. Other times it translates to ease or sustainability. Big impact, given your limited capacity, is the goal of productivity.
From: What’s the Point of Productivity? - Scott H Young