Who said "A warrior's truest battle is within himself."?

This quote is attributed to Grey Worm.

A warrior's truest battle is within himself. - Grey Worm

"A warrior's truest battle is within himself."

Grey Worm Motivation

"I am Grey Worm. I have no name."

"Unsullied do not fear death."

"We are the dragons' soldiers."

"A soldier's duty is to obey."

"I believe in working hard for what you want."

"Never underestimate the power of determination."

"I don't need a reason to fight."

"The most important thing is the mission. Nothing else matters."