Who said "The strongest opponent is always yourself."?

This quote is attributed to Zoro.

The strongest opponent is always yourself. - Zoro

"The strongest opponent is always yourself."

Zoro Wisdom

"I am not going to die. I'm going to keep fighting until I become the world's greatest swordsman!"

"Shitty glasses."

"I don't care what the world thinks. I'm going to be the world's greatest swordsman!"

"A swordsman's true path is one of solitude."

"I'm not angry, I'm just disappointed."

"The best things in life are free."

"You can't have everything in life, but you can have what matters most."

"A woman's intuition is rarely wrong."