It is a practical overview of the business world. Personality is one of the most important field of study in order to become a good manager.
A manager has to deal with several people everyday each having a different personality type. If the manager is not good at handling different personality types then he/she can't be called a good manager.
Apart from that one needs to identify his/her own personality type so that one can understand his/her own needs and the problems related to their own personality type. Then taking appropriate steps to overcome those hindrances.