Here's one relevant quote from the Memorabilia:
ὁρῶ γὰρ ὥσπερ τὰ τοῦ σώματος ἔργα τοὺς μὴ τὰ σώματα ἀσκοῦντας οὐ δυναμένους ποιεῖν, οὕτω καὶ τὰ τῆς ψυχῆς ἔργα τοὺς μὴ τὴν ψυχὴν ἀσκοῦντας οὐ δυναμένους.
As those who do not train the body cannot perform the functions proper to the body, so those who do not train the soul cannot perform the functions of the soul. (https://en.wikiquote.org/wiki/Memorabilia_(Xenophon))
Here's one relevant quote from the Memorabilia:
ὁρῶ γὰρ ὥσπερ τὰ τοῦ σώματος ἔργα τοὺς μὴ τὰ σώματα ἀσκοῦντας οὐ δυναμένους ποιεῖν, οὕτω καὶ τὰ τῆς ψυχῆς ἔργα τοὺς μὴ τὴν ψυχὴν ἀσκοῦντας οὐ δυναμένους.
As those who do not train the body cannot perform the functions proper to the body, so those who do not train the soul cannot perform the functions of the soul. (https://en.wikiquote.org/wiki/Memorabilia_(Xenophon))