Our virtues are usually only vices in disguise.

[Nos vertus ne sont le plus souvent que des vices déguisés]

François VI, duc de La Rochefoucauld (1613-1680) French epigrammatist, memoirist, noble

Réflexions ou sentences et maximes morales [Reflections; or Sentences and Moral Maxims], Epigraph (1675 ed.) [tr. Tancock (1959)]
    (Source)

Added as an epigraph to the entire work in the 4th (1675) edition. A common theme in La Rochefoucauld's work, and variations of this maxim (and related thoughts) had been in the preceding editions and even this and later (see also ¶442).

(Source (French)). Alternate translations:

Our Vertues are oftentimes in Reality no better than Vices disguised.
[tr. Stanhope (1694)]

Our virtues are most frequently but vices disguised.
[tr. Bund/Friswell (1871)]

Our virtues are mostly but vices in disguise.
[tr. FitzGibbon (1957)]

Our virtues, most often, are only vices disguised.
[tr. Whichello (2016)]