Let not these things thy least concern engage;
For though thou fret, they will not mind thy rage.
Him only good and happy we may call
Who rightly useth what doth him befall.
 
[τοῖς πράγμασιν γὰρ οὐχὶ θυμοῦσθαι χρεών:
μέλει γὰρ αὐτοῖς οὐδέν: ἀλλ᾽ οὑντυγχάνων
τὰ πράγματ᾽ ὀρθῶς ἂν τιθῇ, πράσσει καλῶς]

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

Bellerophon [Βελλεροφῶν], frag. 287 (TGF) (c. 430 BC) [Morgan (1718)]
    (Source)

Quoted in Plutarch, "De Tranquilitate Animi [On the Contentedness of the Mind]," sec. 4. (467a). Nauck frag. 287, Barnes frag. 132, Musgrave frag. 24.

(Source (Greek)). Alternate translations:

Nor ought we to be angry at Events;
For they our anger heed not: but the man
Who best to each emergency adapts
His conduct, will assuredly act right.
[tr. Wodhull (1809)]

Events will take their course, it is no good
Our being angry at them; he is happiest
Who wisely turns them to the best account.
[tr. Shilleto (1888), frag. 298]

It does no good to rage at circumstance;
Events will take their course with no regard
For us. but he who makes the best of those
Events he lights upon will not fare ill.
[tr. Helmbold (1939)]

There is no point in getting angry at circumstances. They are uncaring, utterly unconcerned.
But a man who responds to them in the right way, he fares well.
[tr. Stevens (2012)]

One should not get angry with affairs, for they show no concern; but if a man handles affairs correctly as he encounters them, he fares well.
[tr. Collard, Hargreaves, Cropp (1995)]