Follow-through is the cornerstone of execution, and every leader who’s good at executing follows through religiously. Following through ensures that people are doing the things they committed to do, according to the agreed timetable. It exposes any lack of discipline and connection between ideas and actions, and forces the specificity that is essential to synchronize the moving parts of an organization. If people can’t execute the plan because of changed circumstances, follow-through ensures they deal swiftly and creatively with the new conditions.
From "Execution: The Discipline of Getting Things Done" by Larry Bossidy and Ram Charan