Nothing flourishes for ever; each generation gives place to its successor.

[Nihil enim semper floret; aetas succedit aetati.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher

Philippics [Philippicae; Antonian Orations], No. 11, ch. 15 / sec. 39 (11.15/11.39) (43-02 BC) [ed. Harbottle (1897)]
    (Source)

(Source (Latin)). Other translations:

For there is nothing which flourishes for ever. Age succeeds age.
[tr. Yonge (1903)]

For nothing is for ever flourishing; age succeeds to age.
[tr. Ker (Loeb) (1926)]