An analogy came to mind a couple weeks back that has started to reshape the way I think about my calendar: My time slots have potential energy.

Imagine a marble perched up on the edge of a wall. If the marble rolls forward over the edge, it falls all the way down to the floor below. On the other side of the wall is a staircase. If the marble rolls backward down the staircase, it impacts each step individually until finally reaching the floor.

The potential energy between the marble’s original starting place and the floor is the same regardless of whether the marble travels forward over the edge or backward down the steps. The difference is whether that potential is converted into a series of small impacts or a single big one.

In my calendar app, the day and week views are vertically stacked; the day starts at the top and ends at the bottom. Time, like the marble, moves downward. Each event or obligation on my calendar is a surface the marble will impact. On days where my schedule is packed with meetings or chopped up with context switches, my calendar looks a lot like the staircase: many shallow boxes stacked fairly close to each other. On days where I have large, uninterrupted time blocks, my calendar is more like the steep drop off the wall. One big, open space to pick up speed and generate maximum impact.

As my career has progressed, my schedule has shifted from the maker’s schedule to the manager’s schedule. But I believe more than ever that the ability to consistently deliver high quality, valuable work is born of seeds planted and nurtured in large blocks of deep focus time, even if the fruit happens to be harvested later during a shallow block of time. This need for regular deep focus time is why Bill Gates takes regular think weeks, and why John Carmack periodically goes on solo programming retreats to do nothing but work on whatever is the top focus in his mind.

Finally, I think what makes this analogy so potent to me is that potential energy is not guaranteed impact. The size of a time block on my calendar is roughly a cap on the maximum possible impact I can generate from that time. It’s up to me to leverage the time efficiently—to reduce frictional losses. Imagine if the marble dropped off the wall into a pool of water. The marble would lose energy pushing through water the whole way down, dramatically reducing the final impact on the floor. If I am not careful to make efficient use of my deep focus blocks, I will similarly bleed off energy on things that do not help me achieve my ultimate goal.