Proverb: if you clear your mind of passions and attachments, even fire will seem cool — meaning that with mental detachment you can endure hardships.
彼は入試のプレッシャーに負けそうだったが、師匠に『心頭滅却すれば火もまた涼し』と言われて落ち着いた。
He was about to be overwhelmed by exam pressure, but his teacher told him 'if you clear your mind even fire seems cool,' and he calmed down.
登山中の厳しい状況でも、『心頭滅却すれば火もまた涼し』の気持ちで乗り切った。
Even in the harsh conditions while climbing, I got through it with the mindset of 'if you clear your mind, even fire feels cool.'