Who said "The mind is like a river; it must always be flowing."?

This quote is attributed to Bruce Lee.

The mind is like a river; it must always be flowing. - Bruce Lee

"The mind is like a river; it must always be flowing."

Bruce Lee

Martial Artist and Actor Hong Kong-American 1940–1973

"Do not pray for an easy life, pray for the strength to endure a difficult one."

"Be like water."

"It is not the mountain we conquer, but ourselves."

"A man who conquers himself is greater than one who conquers a thousand men in battle."