Act only according to that maxim whereby you can, at the same time, will that it should become a universal law.

see: https://en.wikipedia.org/wiki/Categorical_imperative

it diminishes the empathy and care you're willing to provide for others and maybe even worse it puts you into a never-ending rat race that you ultimately can't win, which is the point of most of these quotes. Greed just tends to cause more greed, with no tranquillity in sight.

It's not even a super deep insight or anything but it's still surprising how little attention it gets.

I think this is all a way of saying "don't wait for Judgment Day to get your shit together."

Having the most fun before death, everyone and everything else be damned?