Desire to appear clever often prevents our becoming so.

[Le désir de paraître habile empêche souvent de le devenir.]

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

Réflexions ou sentences et maximes morales [Reflections; or Sentences and Moral Maxims], ¶199 (1665-1678) [tr. Tancock (1959)]
    (Source)

Found in the 1st (1665) ed. In manuscript, it added:

... parce qu’on songe plus à le paroître aux autres qu’à être effectivement ce qu’il faut être.   [... because we think more about appearing so to others than actually being what we must be.]

The theme of seeming/appearing runs all through La Rochefoucauld's maxims. See also ¶127, ¶134, ¶245, ¶431, ¶457.

(Source (French)). Other translations:

The desire to be thought a wise Man, oftentimes hinders ones coming to be really such.
[tr. Stanhope (1694), ¶200]

The desire of appearing to be persons of ability often prevents our being so.
[pub. Donaldson (1783), ¶1, ed. Lepoittevin-Lacroix (1797), ¶190]

Never are we made so ridiculous by the qualities we have, as by those we affect to have. An affectation of wisdom often prevents our becoming wise.
[ed. Carvill (1835), ¶19]

The desire of appearing clever often prevents our becoming so.
[ed. Gowens (1851), ¶208]

The desire to appear clever often prevents our being so.
[tr. Bund/Friswell (1871), ¶199; tr. Stevens (1939), ¶199]

The desire to appear clever often prevents a man from being so.
[tr. FitzGibbon (1957), ¶199]

The desire to seem clever often prevents our being so.
[tr. Kronenberger (1959), ¶199]

The desire to appear intelligent, often prevents us from actually becoming so.
[tr. Whichello (2016) ¶199]