And if now (but may the immortal gods avert the omen!) that worst of fates shall befall the republic, then, as brave gladiators take care to perish with honor, let us too, who are the chief men of all countries and nations, take care to fall with dignity rather than to live as slaves with ignominy.

[Quodsi iam, quod di omen avertant! fatum extremum rei publicae venit, quod gladiatores nobiles faciunt, ut honeste decumbant, faciamus nos principes orbis terrarum gentiumque omnium, ut cum dignitate potius cadamus quam cum ignominia serviamus.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher
Philippics [Philippicae; Antonian Orations], No. 3, ch. 14 / sec. 35 (2.14/3.35.3) (44-12-20 BC) [tr. Yonge (1903)]
    (Source)

(Source (Latin)). Other translations:

But if already -- may the Gods avert the omen! -- the State has been brought to its latest pass, let us, the leaders of the world and of all nations, do what stout gladiators do to die with honour, let us fall with dignity rather than serve with ignominy. [tr. Ker (Loeb) (1926)]

If -- may the Gods avert the omen! -- the final episode in the history of the Res publica has arrived, let us behave like champion gladiators: they meet death honorably; let us, who stand foremost in the world and all nations, see to it that we fall with dignity rather than serve with ignominy.
[tr. Manuwald (2007)]

But if, may the Gods avert the omen, final fate has come to the State, let us, leaders of the world and all nations, do what noble gladiators do to die with dignity: let us fall on our sword rather than serve with ignominy.
[tr. Wiseman]