Why does Atticus say that Mrs. Dubose is an example of what real courage is?

Atticus tells the children that she was a morphine addict. Jem and Scout's visits helped break her from her morphine addiction, which the doctors had prescribed for her as a painkiller for her illness. Atticus explained to his children that Mrs. Dubose is an example of true courage. Even though she knew she was going to die, Mrs. Dubose wanted to be free of her addiction. Atticus tells Jem that courage is about more than men with guns. Instead, it is about knowing you're going to lose but sticking to your views and fighting anyway. Mrs. Dubose won, because she died beholden to nothing. Atticus calls her "the bravest woman I ever knew."