Everyone who’s psychologically normal thinks they’re the hero.
Will Storr, The Science of Storytelling (2020, p. 95)
What does the protagonist stand to lose if he does not get what he wants? More specifically, what’s the worst thing that will happen to the protagonist if he does not achieve his desire?
Robert McKee, Story: Substance, Structure, Style, and the Principles of Screenwriting (2010, p. 149)

When the author has a clear-cut premise, it is child’s play to find the character who will carry the burden of that premise.
Lajos Egri, The Art of Dramatic Writing: Its Basis in the Creative Interpretation of Human Motives (1942, p. 103)
…women, female-identified, and nonbinary characters can be heroes. Men, male-identified, and nonbinary characters can be heroines.
Gail Carriger, The Heroine’s Journey (2020, p. xv)
The hero of the tale may be one of two types: (1) if a young girl is kidnapped, and disappears from the horizon of her father (and that of the listener), and if Iván goes off in search of her, then the hero of the tale is Iván and not the kidnapped girl. Heroes of this type may be termed seekers. (2) If a young girl or boy is seized or driven out, and the thread of the narrative is linked to his or her fate and not to those who remain behind, then the hero of the tale is the seized or banished boy or girl. There are no seekers in such tales. Heroes of this variety may be called victimized heroes…There is no instance in our material in which a tale follows both seeker and victimized heroes.
Vladimir Propp, The Morphology of the Folktale (1968, p. 36)
The Heroine’s Journey is a separate narrative structure from the Hero’s Journey. It exists. It has always existed. It is not derivative of, nor sourced in, the Hero’s Journey. I thought, for a really long time, that everyone knew this.
I was wrong.
Gail Carriger, The Heroine’s Journey (2020, p. xi)

At this point a more exact definition of the hero may be given than was done before. The hero of a fairy tale is that character who either directly suffers from the action of a villain in the complication (the one who senses some kind of lack), or who agrees to liquidate the misfortune or lack of another person.
Vladimir Propp, The Morphology of the Folktale (1968, p. 50)
A heroine not only asks for help, she is good at it.
Gail Carriger, The Heroine’s Journey (2020, p. 271)
For experts to be taken seriously in public life, they must embody the main traits of heroes…competent…innocent…and influential…Competence is a form of strength, innocence a form of goodness, and influence perhaps a form of activity.
James M. Jasper, Michael P. Young, and Elke Zuern, Public Characters: The Politics of Reputation and Blame (2020, p. 175)
Again, it’s important to remember that when you’re writing a screenplay, the main character must be active; she must cause things to happen, not let things happen to her.
Syd Field, Screenplay: The Foundations of Screenwriting (2005, p. 69)
A character in a drama who isn’t reacting, making decisions, choosing and trying somehow to impose control on the chaos isn’t truly a protagonist.
Will Storr, The Science of Storytelling (2020, p. 189)