It’s not a proverb so much as an expression of disdain or indifference. In common usage, only the first two words are used—with a suitable expression of boredom or nonchalance, while pointedly not looking away from whatever you’re doing at that moment: שמחת זקנתי… (Simhat zqenti…)
Literally, it means, ‘My old woman’s happiness for all to see’, and is a translation of the Ladino (Judaeo-Spanish) expression, La gracia di tu mana (‘Your mother’s happiness’)—i.e., ‘[That might make my mother happy, but] I couldn’t care less’.
[A2A] One would use a calque (a.k.a. loan translation) when there is no equivalent word or expression in the target language, but it captures the meaning so well and concisely that one is moved to recreate it by emulating the same word combination using native words in the target language.
In Hebrew, noted examples are:
By ‘us’ I’m assuming you mean the Jewish people, and specifically those living in Israel today.
You can’t cherry-pick God’s promises. Even if you accept those verses at face value, the promise is contingent upon the nation remaining faithful to God’s commandments. In the Book of Deuteronomy (chap. 28), God warns Moses: