Why are lessons learned important for project management?

PMP is process of progressive evolution,  as human we learn from our mistake, whereas lesson learned are not only record of our mistake to guide us in future  to avoide such mistakes,  but it is also a record of our good practices which can be repeated again to bring the similar positive results. This is why keeping record of good and bad practice definitely provide enough data to a project manager to act in similar situations accordingly with a reference. 

Benefits of lessons learnt:

1. The project team will use the lessons learnt to prevent similar issues from occuring in future assignments/projects which improve the performance of the project and team.

2. Lessons learnt from a project will be stored as "Organization process assets" which will be made available for all future similar projects throughout the organization.

So, it is useful and a recommended action from most of the companies to document the lessons in the project closing process.

• Identifying the project successes/failures.
• Recommendations to improve future performances on projects.