For those interested, sisu is a Finnish apparently untranslatable word meaning being brave, courageous, standing upright and being strong (thanks, Bob Dylan) against adversities (more than "just" extreme polar weather). A life philosophy, love it.
The English language uses "Finnish" only as an adjective but not as a noun. It would also mean that the words that end the Finnish sentence are both adjectives and that would require having a comma between them. Even with the comma there it would sound like a line from a song or a poem. :)
"A stoic determination to persevere in the face of adversity"? Next you'll want sauna translated into English. "An enclosed structure lined with wood heated by hot stones". It's ridiculous. Just accept that some Finnish words don't lend themselves to simple English translations. It's true in other languages as well. There are a number of French words/phrases that have been adopted into English.