Stobaeus on Stoic Ethics 12

And the Stoics also say that the wise man does everything which he does well—obviously. 

For in the sense that we say that the flute player or kithara player does everything well, it being understood that we refer to what the one does in his flute playing and the other in his kithara playing, in the same sense we say that the prudent man does everything well, both what he does and, by Zeus, what he does not do too. 

For they thought that the opinion that the wise man does everything well follows from his accomplishing everything in accordance with right reason and, as it were, in accordance with virtue, which  is a craft concerned with one’s entire life. 

Analogously, the base man too does everything which he does badly and in accordance with all the vices.