Worry. To Hermione, it was a funny word. The dictionary described it as "to torment oneself with or suffer from disturbing thoughts. She knew the meaning of the word quite well, actually; all those years of worrying about her grades, about Harry, and about Ron. But had she ever tormented herself with disturbing thoughts?
This year, everything was different. Since the return of Voldemort, the wizarding world had not been the same. Worry had been the underlying emotion all summer. It was everywhere. In Mrs. Weasley as she went about making the house habitable. In Mr. Weasley as he came and went from 12 Grimmauld place, leaving for work at the Ministry or other various responsibilities he had. In Professor Lupin when he would come to the house for meetings, or just to say hello to Sirius. And most of all, in Harry.
The weight of the world had been placed on Harry's shoulders. He was the reason Voldemort had returned, but he was also the reason Voldemort had been defeated in the first place. The entire wizarding world looked to Harry to save them again, to defeat Voldemort one more time. He was, after all, the boy who lived.
And it was in that fact that most of her worries rest. Harry was her best friend; one of the first friends she had ever really had. She had always tried her best to be there when he needed her. To help him whenever she could, abandoning her reluctance to break the rules in favor of her desire for him to be safe.
Harry was the boy who lived, and what worried Hermione the most was that he wouldn't remain that way for long.