The one you chose and the one that arrived

Two interruptions of equal length are not equal at all.

There is a meaningful difference between stopping because you decided to stop and stopping because something reached in and stopped you. When you choose the break, you get to close the loop first: finish the sentence, note where you were, leave yourself a handhold. When it arrives from outside, you are pulled out mid thought with nothing marked. The first is a pause. The second is a break in the middle of a load bearing beam.

This distinction matters more than the total number of interruptions, and it is more actionable. You are rarely able to reduce interruptions to zero, and trying tends to fail. What you can often do is convert some of them from arriving to chosen: gathering things so they are dealt with together, deciding when you will look rather than being told, ending a stretch at a point you selected rather than a point somebody else selected for you.

The same logic explains why the last few minutes of a work session are worth more than they look. Spending two of them writing down where you got to and what comes next removes most of the entry cost when you return. It feels like an odd use of the final minutes. It is one of the few reliable ways to make the next stretch cheaper to begin.