The plans can fail because
- either the design was not adequate and complete, missing some vital elements that would affect input or process or output, OR
- it was not implemented the way it was designed, OR
- some of the external environmental factors did not behave as expected in the plan design, OR
- perhaps the target was too high vis-a-vis planned or available resources.
But the mission is what the plan aims to achieve. The mission can undergo change, as it should, ordinarily.
One may give up the mission. but, that still is not mission’s [intrinsic ] failure. It is the failure of that individual who had dreamed that mission.