Interesting. As a non-native speaker I wasn't really aware of this meaning of the word "grit", but it seems very similar to the concept of "sisu" [1] in Finnish, often regarded as an integral part of the national character of Finns and considered very difficult if not impossible to translate exactly. Wikipedia does list "grit" as one of the mental characteristics "sisu" can be thought to be a combination of.

[1] https://en.wikipedia.org/wiki/Sisu