Ἡ πεῖρα διδάσκαλος.
Experience is a teacher.
You can find the saying in Gregory of Nyssa, and likewise in John Chrysostom. Plus here's a fun word origin: from Greek πεῖρα and its derivative, πειρατής, we actually get the English word pirate! We also get technical terms like empirical.
Κύκνειον ᾆσμα.
A swan song.
You've seen another version of this saying in a previous post: Κύκνειον μέλος. The legend of the song that the swan (supposedly) sings just before it dies, having spent the rest of its life in silence, has its own article at Wikipedia: Swan song. The word ᾆσμα is from the verb ἀείδω, "sing," while μέλος has a more general meaning: it is a "part" or "limb" of a larger whole, and then comes to mean specifically a "tune" or "song."
Ὄφεως ὄμμα.
The eye of a snake.
This proverbial phrase refers to someone who has a particularly sharp and piercing gaze.
Γνῶθι σεαυτόν.
Know yourself.
You can read about this Delphic maxim at Wikipedia: Know thyself. You will also find this form of the saying: Γνῶθι σαυτόν, as in this Roman mosaic, which uses the saying as a kind of "memento mori."
Ἄκουε πάντα.
Listen to everything.
This is one of the Delphic maxims recorded by Stobaeus. Notice the accusative object, πάντα. That means ἄκουε has the sense of "listen to," as in listening to things, to sounds heard. When ἀκούω takes the genitive, it has the sense of "hearing" a person, and even "hear and obey."
And to finish up, here's a random proverb and a random LOLCat too:
