Who said "The greatest teacher is often our greatest adversary."?

This quote is attributed to Rhaegar Targaryen.

The greatest teacher is often our greatest adversary. - Rhaegar Targaryen

"The greatest teacher is often our greatest adversary."

Rhaegar Targaryen Education

"The dragon has three heads."

"I have a duty to my realm and to the future."

"Music is the voice of the soul."

"Love is the most powerful force in the world."

"Education opens doors."

"Education opens doors to endless possibilities."

"I ain't got the education you got, bub."

"You can't put a price on history."