Wherefore, we must not think it sufficient that we do any thing merely well; but we ought to make it our study to do every thing gracefully also.

[Non si dèe adunque l’uomo contentare di fare le cose buone, ma dèe studiare di farle anco leggiadre.]

Giovanni della Casa (1503-1556) Florentine poet, author, diplomat, bishop

Galateo: Or, A Treatise on Politeness and Delicacy of Manners [Il Galateo overo de’ costumi], ch. 28 (1558) [tr. Graves (1774)]
    (Source)

(Source (Italian)). Alternate translations:

It is not inoughe for a man, to doe things that be good: but hee must also have a care, hee doe them with a good grace.
[tr. Peterson (1576)]

Therefore, a man must not be content with doing what is good, but he must also seek to do it gracefully.
[tr. Einsenbichler/Bartlett (1986)]

A man must therefore not be content to do things well, but must also aim to do them gracefully.