Calendars protect important things, yet they can also turn rest into a sequence of appointments. A free hour is different from a scheduled activity labeled relaxation. It has no assigned outcome and therefore no way to be completed badly.
Protecting that hour requires a boundary. Put it between obligations rather than at the end of a list that may never finish. Silence routine notifications and resist filling the space in advance with errands disguised as leisure.
At first, the mind may reach automatically for a screen. Pause long enough to notice what is actually wanted: a nap, a walk, music, coffee with a neighbor, repairing something, or doing nothing visible at all. The choice can remain small.
Parents, carers, and people working multiple jobs may not control a full uninterrupted hour. The principle still scales. Ten unclaimed minutes, exchanged fairly with another person, can restore a sense that every part of the day is not already owned.
Unplanned time is not a productivity technique, though it may improve work later. Its value is more direct. It reminds a person that attention can be inhabited, not only allocated.