Who said "Progress comes not from comfort, but from struggle."?

This quote is attributed to Jack London.

Progress comes not from comfort, but from struggle. - Jack London

"Progress comes not from comfort, but from struggle."

Jack London Perseverance

Novelist American 1876–1916

"The proper function of man is to live, not to exist."

"I would rather be ashes than dust."

"You can't wait for inspiration. You have to go after it with a club."

"The wise man doesn't give the right answers, he possesses the right questions."

"Perseverance is the key to success."

"Don't give up on what you believe in."

"I've been through worse."

"You learn to live with the pain."