Sweet is the remembrance of troubles when you are in safety.

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

Andromeda [Ἀνδρομέδα], Frag. 131 (TGF) (412 BC)
    (Source)

(Source (Greek)). Alternate translations:

'Tis sweet to recollect past toils in safety.
[tr. Wodhull (1809)]

Sweet is the memory of toils that are past.
[tr. Reid (1883), in Cicero, De Finibus, 2.105]

Sweet is the memory of sorrows past.
[tr. Rackham (1914), in Cicero, De Finibus, 2.105]