Who said "Sometimes a man must be alone to truly know himself."?

This quote is attributed to Oberyn Martell.

Sometimes a man must be alone to truly know himself. - Oberyn Martell

"Sometimes a man must be alone to truly know himself."

Oberyn Martell Solitude

"I am the viper. When the time comes, I will strike."

"Elia of Dorne. My sister. You raped her. You murdered her children."

"I want to look the man in the eye and see the fear in his heart."

"The man who passes the sentence should swing the sword."

"Sometimes being the best means being the loneliest."

"Solitude gives us time to reflect on what matters"

"I'm not good with people, never have been."

"I feel like I'm disappearing."