Hicks: Moreover, he who has once become wise never more assumes the opposite habit, not even in semblance, if he can help it.
Yonge: Also, that a man who has once been wise can never receive the contrary disposition, nor can he of his own accord invent such a state of things as that he should be subjected to the dominion of the passions; nor can he hinder himself in his progress towards wisdom.
Hicks: He will be more susceptible of emotion than other men: that will be no hindrance to his wisdom.
Yonge seems to include the emotions and their non-hindrance with the above. i.e., the wise one will not let the passions hinder progress towards wisdom once they’ve become wise.
The original text per Perseus Digital Library is:
ἀλλὰ καὶ τὸν ἅπαξ γενόμενον σοφὸν μηκέτι τὴν ἐναντίαν λαμβάνειν διάθεσιν μηδὲ πλάττειν ἑκόντα: πάθεσι μᾶλλον συσχεθήσεσθαι: οὐκ ἂν ἐμποδίσαι πρὸς τὴν σοφίαν. Which is composed of three clauses:
ἀλλὰ καὶ τὸν ἅπαξ γενόμενον σοφὸν μηκέτι τὴν ἐναντίαν λαμβάνειν διάθεσιν μηδὲ πλάττειν ἑκόντα:
Literally: Also, the once-arisen sage will no longer fall back to the opposite disposition nor be put into that mold wittingly (on purpose).
πάθεσι μᾶλλον συσχεθήσεσθαι:
Literally: By the pathē they will exceedingly be affected...
οὐκ ἂν ἐμποδίσαι πρὸς τὴν σοφίαν.
Literally: This will not be a hindrance on the path to wisdom.
However, the digitized manuscript has:
αλλὰ καὶ τὸν ἅπαξ γενόμενον σοφὸν, μηκέτι τὴν ἐναντίαν λαμβάνειν διάθεσιν· μηδὲ πλάττειν ἑκόντα πάθεσι μᾶλλον συσχεθήσεσθαι· οὐκ ἂν ἐμποδίσαι πρὸς τὴν σοφίαν.
The manuscript then gives five different clauses or phrase:
αλλὰ καὶ τὸν ἅπαξ γενόμενον σοφὸν,
Literally: Once one has become wise… (the once-arisen sage)
μηκέτι τὴν ἐναντίαν λαμβάνειν διάθεσιν·
Literally: ... will no longer fall back to the opposite disposition...
μηδὲ πλάττειν ἑκόντα πάθεσι μᾶλλον συσχεθήσεσθαι·
Literally: .. nor (μηδέ) be put into (that) mold readily/wittingly by the πάθη to be exceedingly affected…
Συσχεθήσεσθαι: future infinitive “to be constrained, distressed, afflicted, and, generally, to be affected by anything whether in mind or body”
οὐκ ἂν ἐμποδίσαι πρὸς τὴν σοφίαν.
Literally: .. This would not impede/hamper/fetter (their way) toward wisdom.
This section appears to mean that the sage will not be exceedingly affected by the passions, emotions, etc., that they won't be overcome with emotion and this is not an impediment on the way to wisdom.
I am more inclined to take Hicks's interpretation as the text being two separate ideas. This appears to flow better:
The sage, once wise, won't fall back into ignorance, nor will they willingly do this on purpose.
Sages are greatly affected by the pathē (i.e., more so than other people) but this doesn't hinder their progress to wisdom.
Trivia: ἐμποδίσαι literally means "to have one's feet bound, to be put in fetters."