Ah, but the argument is...
At the end of your life, you're dead. Any "accomplishments" you have cease to matter. Unless you're one of the few lucky folks who get remembered for centuries, you'll get forgotten before long. Nothing you do will last. Your children will pass. Their children will pass, until eventually your descendants don't even know your name, if your line doesn't die out. Anything you build materially will be destroyed. Your comfortable, cautious life will have amounted to nothing.
What, then, has meaning? What has meaning in your life?
The one thing that will never go away: the fact that AT THAT MOMENT you enjoyed your life to the fullest. Because your MOMENTARY enjoyment will never cease to have been. The passing of time does not erase a past moment. Caution leads to a continuation of moments of mediocrity, that in the end mean nothing. Risk-taking leads to a continuation of moments of AWESOME, that in the end still mean nothing, but you got to be AWESOME.
I lied, that's not THEIR argument. That's MY argument. THEIR argument is, yeah, basically "**** it, it feels good and seems like a good idea in my inebriated state right now"
I like my argument better. "Je ne regrette rien" > YOLO, if only because it's French and thus classier.