Being productive is not about being busy, but rather working on valuable things. Knowing what to focus on is an important skill, in particular when faced with the seemingly unending lists of things to do everyone has between work and personal life.
The focusing question is a tool to help with prioritization introduced by Gary W. Keller in his book "The ONE Thing".
What is the single thing that I can do for
<x>so that everything else will become easier or unnecessary?
It might seem like a simple question. Let's take it apart to see how powerful it is.
"What is the single thing that I can do..." By framing the question in the realm of things that can be done rather than could be done it forces you think in actionable terms. It also requires you to pick one and only one.
<x>..." Stating out the object of your focus ensures you don't trail off in other directions.
"...so that everything else will become easier..." Once you have a list of actions to take you should find the ones with the biggest return of investment.
"...or unnecessary." This last part is easy to miss, but very important. Considering what could make everything else unnecessary forces you to think bigger picture. The best way to solve a problem is not to have it.
Starting the work day by applying the focusing question to the projects you are working on is a way to stay on track and deliver in time, if not earlier. The time spent considering the different options will pay off. It will identify the actions that will make the biggest impact.
When working on big projects in a team it's easy to get sucked into our own parts. Software developers like to code, designers like to design. Shifting the point of view from "what's the next item in my backlog" to "what can I do that will make completing this project easier or unnecessary" will often push you to get outside of your comfort zone.
The next action with the most impact might be touching base with another team, double down on manual testing to discover edge cases, or prepare a showcase to ensure the progress is in line with what's expected.
You are the sum of your actions. Being able to take ones that are the most effective with consistency is guaranteed to help achieving better results sooner. Using the focusing question is one way to identify such impactful actions.