If we did not flatter ourselves, the flattery of others could do us no harm.

[Si nous ne nous flattions point nous-mêmes, la flatterie des autres ne nous pourroit nuire.]

François VI, duc de La Rochefoucauld (1613-1680) French epigrammatist, memoirist, noble
Réflexions ou sentences et maximes morales [Reflections; or Sentences and Moral Maxims], ¶152 (1665-1678) [tr. Kronenberger (1959)]
    (Source)

Present in the 1st (1665) edition, where it ended with "... ne nous feroit jamais de mal." See also maxim ¶158.

(Source (French)). Other translations:

If we did not Flatter our selves, all the Flatteries of other People could never hurt us.
[tr. Stanhope (1694), ¶153]

Did we not flatter ourselves, the flattery of others could never hurt us.
[pub. Donaldson (1783), ¶144; ed. Lepoittevin-Lacroix (1797), ¶146]

Were we not to flatter ourselves, the flattery of others would never hurt us.
[ed. Carvill (1835), ¶127]

If we did not flatter ourselves, the flattery of others would be very harmless.
[ed. Gowens (1851), ¶155]

If we never flattered ourselves the flattery of others would not hurt us.
[tr. Bund/Friswell (1871), ¶152]

Did we not flatter ourselves, the flattery of others could not harm us.
[tr. Heard (1917), ¶152]

Flattery would do us no harm if we did not flatter ourselves.
[tr. Stevens (1939), ¶152]

If we never flattered ourselves, we would be immune to the flattery of others
[tr. FitzGibbon (1957), ¶152]

If we never flattered ourselves the flattery of others could do us no harm.
[tr. Tancock (1959), ¶152]

If we did not flatter ourselves, the flattery of others could never harm us.
[tr. Whichello (2016) ¶152]