The friends of the warrior of light ask him where he draws his energy from. He says: “From the hidden enemy.”
His friends ask who that is.
The warrior responds: “Someone we can no longer hurt.”
It might be a boy who beat him in a childhood scrap, the girlfriend who left him when he was eleven, the teacher who said he was stupid. When he is tired, the warrior reminds himself that these enemies have still not seen his courage.
He does not consider revenge, because the hidden enemy is no longer part of his story. He thinks only of improving his skills so that his deeds will be known throughout the world and reach the ears of those who have hurt him in the past.
— Manual Of The Warrior Of Light by Paulo Coelho