I suppose the cultural equivalent would be writing Velle est posse instead of "When there is a will, there is a way." Latin is fancier! (And has age and prestige going for it.)
Explanation on Grass' skill text
They tiny ㇾ in the text is a "reverse mark" telling the reader to reverse the reading of 不 and 成 (i.e. "read 成 first") because negation comes after the verb in Japanese (unlike in Chinese).
In-game Grass' skill is written as 精神一到何事か成らざらん, which already has the Classical Chinese 'translated' into semi-classical Japanese (which is how you're supposed to read the kanbun text anyway, for a Japanese reader). This is common with a lot of proverbs that originate from classical Chinese texts. 精神一到，何事不成 in particular is a quotation from Chapter 8 Line 71 of the Zhuzi Yulei, a Song dynasty philosophical text.
TL;DR: El pissed Grass enough for the latter to go full-on CLASSICAL, the whole nine yards.
