The person carrying the map should still listen when the ground disagrees.

A plan is a description made earlier by somebody who was not standing where you are. When the path in front of you fails to match it, the temptation is to trust the document, because it feels authoritative while the ground feels like an inconvenience. Maps go out of date and reality does not. Holding a plan loosely is part of using it well.

When evidence contradicts your plan, say the contradiction out loud rather than working around it; ask what would have to be true for the plan to still be right, and check whether it is.