Whats the most powerful word in a product manager's or founder's vocabulary?

"No."

Its the biggest productivity hack that doesn't get its fair share of love. Productivity is all about getting things done, and the best way to get things done is to have fewer things to do.

Cut down on things to do by saying no to any new feature or stakeholder request that is distracting or not immediately urgent.  Saying no is a simple way of making sure you follow the strategy and vision that you initially laid out and not get bogged down with distractions that might seem cool at the time - but don't serve the overall strategy.

We only have 5 or 6 hours at most of real work hours in a day.  Maximise your productivity on making sure you are working on what needs to be worked on. At the end of the day product management is all about solving problems.  Make sure you are solving the right ones and be brutal with the word "no."