Leave room for the ordinary problem that no detailed plan can schedule.

Plans fail on the small and unremarkable far more often than on the dramatic. A key that will not turn, a queue, a phone call that runs twenty minutes over: none of these can be predicted individually, but something from that family arrives most days. A schedule with no slack treats an average day as a perfect one.

Build in one loose stretch tomorrow and defend it as though it were a meeting. If nothing goes wrong, you get an unexpectedly easy hour. If something does, the day survives it.