As a PM, most systems run due to everyday things people do. It's a mix of Standard Operating Procedure and heroic efforts to deal with the problems with Standard Operating Procedure.

If either of those are disrupted, things fragment. If both are disrupted at the same time for a duration, the system shuts down and can even collapse.

This is honestly why regularity matters. You can do the same old same old AND have the energy for whatever heroic measures correct the dumb things that pop up.