An important consideration for when you are writing or translating is to keep in mind that our sayings might not translate very well, or exist at all in the other language.
In English, we can call someone a smart cookie, but in Spanish, that doesn't really exist. You can do a direct translation: galleta intelligente, but it doesn't convey the meaning you wanted.
Proverbs also have the same difficulties, in English, there is a saying: Don't judge a book by it's cover, but in French, the same proverb is actually L'habit ne fait pas le moine (literally, the clothing doesn't make the monk).
It doesn't even have to be a different language; when writing in English, Canadians, Americans, Brits and Australians all have different expressions that the others might not be familiar with. So be careful!
While some proverbs and sayings are used by many cultures, it could be that the exact wording differs. Or, it could be that that idea doesn't exist in another language/culture. And so, when writing or translating, keep in mind that your idiomatic expressions are culturally, socially and linguistically based and to look up whether that expression has "crossed over".