Waste not fresh tears over old griefs.

Euripides (485?-406? BC) Greek tragic dramatist

Alexander [Ἀλέξανδρος], Frag. 44 (TGF) [Chorus?] (415 BC) [tr. Morgan]
    (Source)

Alternate translations:

Shed not fresh tears for ills of ancient date.
[Fragment: Barnes 47, Musgrave 20]

You must not mourn for old things with fresh tears.
[tr. Yalouris]