If you’ve read The Phoenix Project, then you already know that of the four types of work, unplanned work is the plague for DevOps. It is just that sometimes, this unplanned work for DevOps, is planned work for everybody else. Conway’s Law at its best.
a note on unplanned work
Published
Managing organized complexity 
When you have no plans, unplanned work is planned work. That’s how we work down here.