The word "hero" comes from Greek (heros) and its root means the guardian and defender. A hero of a novel is a person whose life and deeds have a special meaning for the author of the novel and supposedly for us, too. Heroism is defined always in a context, where other people are less or not at all heroic. Heroism is essentially a social quality, a hero impersonates a shared will - of a town, a team, the society, etc. We can see this notion at the 28th chapter of David Copperfield, where a hero is defined against a public trouble:
"With these words, and resisting our entreaties that she would grace the remaining circulation of the punch with her presence, Mrs. Micawber retired to my bedroom. And really I felt that she was a noble woman - the sort of woman who might have been a Roman matron, and done all manner of heroic things, in times of public trouble."
Mrs. Micawber would have been a hero, provided that the circumstances also permitted for her to become one. A hero needs trouble, and a public trouble, at that. Already in antiquity, and especially in the Greek tragedies, a hero was not that much a person who saved the society from a danger, but mainly a person who caused and suffered many dangers himself. In that meaning, a hero seems like a tree on a high mountain: the favourite of the thunders! - to remember Nietzsche's metafor. He is the first and the only one to taste his and our dangers, a person with an exceptional sensitivity, a person that suffers on our behalf. And here we come at the opening, so much quoted, phrases of David Copperfield:
"Whether I shall turn out to be the hero of my own life, or whether that station will be held by anybody else, these pages must show."