Dum differtur vita transcurrit. Omnia, Lucili, aliena sunt, tempus tantum nostrum est; in huius rei unius fugacis ac lubricae possessionem natura nos misit, ex qua expellit quicumque vult. Et tanta stultitia mortalium est ut quae minima et vilissima sunt, certe reparabilia, imputari sibi cum impetravere patiantur, nemo se iudicet quicquam debere qui tempus accepit, cum interim hoc unum est quod ne gratus quidem potest reddere.
I'm thinking "And such is the stupidity of mortal men that those things which are smallest and most worthless, and certainly replaceable, when they [mortals] have acquired them, they [the things] are allowed to be attributed to one's self, [although] nobody would judge himself to owe anything who takes/passes time, when this is the one thing which he cannot happily restore."
The subjunctives for "patiantur" and "iudicet" are tripping me up. As are a number of constructions like "imputari sibi" and "tempus accepit." Also, I'm not sure what to make of "gratus" in this context. Is it functioning adverbially?