It's easy to forget the mission when the task at hand becomes overwhelming. Many times, people's jobs can become too stressful; the workers forget why they are even working in the first place. The point of work is to accomplish the mission, and the point of the mission to move things in a certain direction. If getting caught up in the work starts to become too distracting that it begins to move things in the opposite direction, then it's time to reevaluate either the mission or the workload.