The second person singular is used to designate an imaginary person, as in proverbs:
ψυ_χῆς ἐπιμελοῦ τῆς σεαυτοῦ
a. Hdt. uses the second person in directions to travellers (2. cross30).
See also cross942.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].