Seneca expresses "YOLO" sentiments in 55 A.D.

I am always surprised to see some people demanding the time of others and meeting a most obliging response. Both sides have in view the reason for which the time is asked and neither regards the time itself—as if nothing is being asked for and nothing given. They are trifling with life’s most precious commodity, being deceived because it is an intangible thing, not open to inspection and therefore reckoned very cheap—in fact, almost without any value...

No one will bring back the years; no one will restore you to yourself. Life will follow the path it began to take and will neither reverse nor check its course. It will cause no commotion to remind you of its swiftness, but glide on quietly. It will not lengthen itself for a king’s command or a people’s favor. As it started out on its first day, so it will run on, nowhere pausing or turning aside. What will be the outcome? You have been preoccupied while life hastens on. Meanwhile death will arrive, and you have no choice in making yourself available for that.
 
Can anything be more idiotic than certain people who boast of their foresight? They keep themselves officiously preoccupied in order to improve their lives; they spend their lives in organizing their lives. They direct their purposes with an eye to a distant future. But putting things off is the biggest waste of life: it snatches away each day as it comes, and denies us the present by promising the future. The greatest obstacle to living is expectancy, which hangs upon tomorrow and loses today. You are arranging what lies in Fortune’s control, and abandoning what lies in yours. What are you looking at? To what goal are you straining? The whole future lies in uncertainty: live immediately... And even if you do grasp it, it will still flee. So you must match time’s swiftness with your speed in using it, and you must drink quickly as though from a rapid stream that will not always flow.

You can read more of the essay in the current issue of Lapham's Quarterly.