I recently reread Ecclesiastes & on the second reading came across what people tend to be trying to get at with that advice. I'll try give it from the Ecclesiastes perspective
Whatever you go out & gather, is ultimately worthless. So if you're in a shit mood & thinking that some day this work will pay off, you'll find that your days are spent in a shit mood & thinking some day this work will pay off. & then you die & everything you did doesn't really matter, & you spent your time in a shit mood. So if instead you find enjoyment in the simple daily toll, that your work today is essentially paying for the food you'll enjoy today, then you'll find your days are spent in a good mood. & then you die & everything you did doesn't really matter, but at least you enjoyed your time while it lasted
So "live it like your last" is a bit hyperbolic, but at least don't justify your suffering on the idea that life gets better
To try make sense of "live it like your last", it might be better said as "go to sleep at peace with your life even if you were to die in the night"
Whatever you go out & gather, is ultimately worthless. So if you're in a shit mood & thinking that some day this work will pay off, you'll find that your days are spent in a shit mood & thinking some day this work will pay off. & then you die & everything you did doesn't really matter, & you spent your time in a shit mood. So if instead you find enjoyment in the simple daily toll, that your work today is essentially paying for the food you'll enjoy today, then you'll find your days are spent in a good mood. & then you die & everything you did doesn't really matter, but at least you enjoyed your time while it lasted
So "live it like your last" is a bit hyperbolic, but at least don't justify your suffering on the idea that life gets better
To try make sense of "live it like your last", it might be better said as "go to sleep at peace with your life even if you were to die in the night"