Isocrates is trying to persuade the Athenians to desist from their dreams of power. In the end it only brings ruin.
μέγιστον δὲ τεκμήριον: οὐ γὰρ μόνον ἡμᾶς ἀλλὰ καὶ τὴν Λακεδαιμονίων πόλιν διέφθειρεν, ὥστε τοῖς εἰθισμένοις ἐπαινεῖν τὰς ἐκείνων ἀρετὰς οὐχ οἷόν τ᾽ ἐστὶν εἰπεῖν τοῦτον τὸν λόγον, ὡς ἡμεῖς μὲν διὰ τὸ δημοκρατεῖσθαι κακῶς ἐχρησάμεθα τοῖς πράγμασιν, εἰ δὲ Λακεδαιμόνιοι ταύτην τὴν δύναμιν παρέλαβον, εὐδαίμονας ἂν καὶ τοὺς ἄλλους καὶ σφᾶς αὐτοὺς ἐποίησαν. πολὺ γὰρ θᾶττον ἐν ἐκείνοις ἐπεδείξατο τὴν φύσιν τὴν αὑτῆς: τὴν γὰρ πολιτείαν ἣν ἐν ἑπτακοσίοις ἔτεσιν οὐδεὶς οἶδεν οὔθ᾽ ὑπὸ κινδύνων οὔθ᾽ ὑπὸ συμφορῶν κινηθεῖσαν, ταύτην ἐν ὀλίγῳ σαλεῦσαι καὶ λυθῆναι παρὰ μικρὸν ἐποίησεν.
This is the greatest proof. For not only has it (power) ruined us but also the city of the Lacedaimonians, so those who like to praise their virtues can’t use this argument that we have come to a bad pass because we are a democracy, but if they got hold of power, they would bring prosperity to others as well as themselves. For power revealed its nature far quicker in their case. For no one knows of any change in their constitution during seven hundred years from danger or disaster but power has caused it to be disturbed and all but destroyed.
Isocrates Peace 8.95 355 BC