Most of the IAS aspirants have desire to become an IAS officer. So they work hard day & night, read many books and gain so much of knowledge. It is a good thing but not sufficient to become an IAS officer. You can understand the fact, "Just wearing the dress of a king, one cannot become a king". Similarly without changing the basic nature of your thought process, just covering yourself with the knowledge which is borrowed from books and other sources is not the surest way to be successful in this race.