Courage
"Courage is not a man with a gun in his hand. It's knowing you're licked before you begin but you begin anyway, and you see it through no matter what. You rarely win, but sometimes you do."
~Atticus Finch in To Kill a Mockingbird
"Nevertheless, Harry, while you may have only delayed [Voldemort's] return to power, it will merely take someone else who is prepared to fight what seems to be a losing battle next time--and if he is delayed again and again, why, he may never return to power."
~Albus Dumbledore in Harry Potter and the Sorcerer's Stone