Hope has two beautiful daughters. Their names are anger and courage; anger at the way things are, and courage to see that they do not remain the way they are.
Attr. St. Augustine.
This didn’t meet the “sounds right” test to me–St. Augustine is generally not one for extended metaphors like this. He does do extended similes, but not metaphors.
Wikiquote has this on the talk/disputed page, given a citation from Spirituality and Liberation: Overcoming the Great Fallacy (1988) by Robert McAfee Brown, p. 136. That book happens to be searchable at Google Books, but the alleged quotation is not found there. (Perhaps Google doesn’t have the whole thing searchable.)
I went searching through Google Books for the phrase. It turns up in a lot of books connected with liberation theology (which doesn’t make the attribution false). One of the hits does have a footnote, but it simply cites a somewhat earlier (1987) book and says that there’s no citation given in that book.
I then found another book by Robert McAfee Brown in which he calls it “a reflective comment whose location in the Augustinian corpus I wish I could pinpoint” (Speaking of Christianity, p. 74). In other words, he doesn’t know where it’s from either.
Then I found this from Archbishop Chaput: “The words are apocryphal. There’s no real evidence that Augustine ever wrote them” (Strangers in a Strange Land, p. 162). (He goes on to add, “But their content is clearly true and worth remembering as a guide to Christian discipleship.”)
I poked around a little more but couldn’t find much of anything more helpful. Google Books doesn’t have anything before 1987. Given the amount of negative evidence, I’m not going to try guessing at Latin phrases to search for in Augustine’s work. I’m just going to say that however beautiful and helpful the thought may be (cf. +Chaput, above), it didn’t come from the mind of St. Augustine.