We are held to our duty by laziness and timidity, but often our virtue gets all the credit.
 
[Pendant que la paresse et la timidité nous retiennent dans notre devoir, notre vertu en a souvent tout l’honneur.]

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

Réflexions ou sentences et maximes morales [Reflections; or Sentences and Moral Maxims], ¶169 (1665-1678) [tr. Tancock (1959)]
    (Source)

Appeared in the 1st ed. (1665) as:

While laziness and timidity alone have the merit of keeping us in our duty, our virtue often has all the honour.
 
[Pendant que la paresse et la timidité ont seules le mérite de nous tenir dans notre devoir, notre vertu en a souvent tout l’honneur.]

In the manuscript version this read:

Shame, laziness and timidity alone retain the merit of holding us back from our duty, while our virtue has all the honor.
 
[La honte, la paresse et la timidité conservent toutes seules le mérite de nous retenir dans notre devoir, pendant que notre vertu en a tout l’honneur.]

In a letter to J. Esprit, La Roswchefoucauold phrased it this way:

It must be admitted that virtue, by which we boast of doing everything good that we do, would not always have the strength to hold us back from the rules of our duty, if laziness, timidity, or shame did not make us see the disadvantages of departing from them.
 
[Il faut avouer que la vertu, par qui nous nous vantons de faire tout ce que nous faisons de bien, n’aurait pas toujours la force de nous retenir dans les règles de notre devoir, si la paresse, la timidité, ou la honte ne nous faisoient voir les inconvénients qu’il y a d’en sortir.]

Variations of this sentiment around the hypocrisy of vices serving as virtue show up a lot in La Rochefoucauld's maxims. See the Epigraph, and ¶¶ 1, 200, 205, 218, 220, 237, 241, 253, 266, 354, and 442.

(Source (French)). Alternate translations:

We are many times kept within the limits of our duty by Shame, Sloth, and Timorousness, while in the mean time our Virtue hath all the credit of it.
[tr. Davies (1669), ¶5]

Many People are kept within their Duty, because they have not the Courage, or will not be at the pains of being wicked; and in such cases oftentimes our Vertue runs away with all the Praise.
[tr. Stanhope (1694), ¶170]

Idleness, timidity, and shame, often keep us within the bounds of duty; whilst virtue seems to run away with the honour.
[pub. Donaldson (1783), ¶233; ed. Lepoittevin-Lacroix (1797), ¶163]

Idleness, timidity, or shame, often keeps us within the bounds of duty; whilst virtue seems to run away with the honour of it.
[ed. Carvill (1835), ¶202]

Indolence and timidity often keep us to our duty, while our virtue carries off all the credit of doing so.
[ed. Gowens (1851), ¶172]

Idleness and fear keeps us in the path of duty, but our virtue often gets the praise.
[tr. Bund / Friswell (1871), ¶169]

Although it is frequently laziness and timidity that keep us within the path of duty, it is virtue that reaps the credit.
[tr. Heard (1917), ¶169]

Though indolence and timidity keep us to the path of duty, virtue often gets all the credit.
[tr. Stevens (1939), ¶169]

When laziness or cowardice keeps us to the path of duty, the credit is often given entirely to our honour.
[tr. FitzGibbon (1957), ¶169]

When laziness and timidity yokes us to our duties, we often give virtue the credit for it.
[tr. Kronenberger (1959), ¶169]

While it is idleness and timidity that retain us in our duty, our virtue takes all the credit.
[tr. Whichello (2016), ¶169]