Why was smart Hermione Granger always worrying about doing badly?

Answer 1

Hermione Granger is, by nature, a perfectionist. Her greatest fear is failure. Think about it: at 11 years old, she is contacted by a mysterious "magic school". Already a perfectionist, she takes it up to herself to be the best at whatever she must be at this new place. When she arrives at Hogwarts, people are turned off by this, and she finds herself friendless. Because she already has a fear of failure, she uses her books as an escape, telling herself that people don't matter. After she becomes close with Harry and shares his struggle to find out who is and kill Lord Voldemort, many issues are pressed upon her, combined with increasingly difficult classes and new hormonal issues. Her natural cleverness and perfectionism becomes her refuge once again. Because succeeding academically is the one thing she knows she can do, no matter what, she makes sure that it is not taken away from her by studying increasingly often. She worries about doing badly because if she doesn't succeed, then she has nothing to hold onto during the difficult times ahead.

Answer 2

Because she is a Mud Blood and thinks she is inferior due to other wizards opinions. I think it is a case of low esteem.