“Sing like no one's listening, love like you've never been hurt, dance like nobody's watching, and live like its heaven on earth.”
And on how many think they can recite it.
I like Twain's original much better. I also adapt it for my own "live as if..." advice.
Since yesterday turned out not to be your last and tomorrow is just a theory that you will survive, receive today as a gift. But if you choose work that is worth carrying on and if you plan it and do it in community, then you may plan as if you will live for ever.
A dread of being trite is a hobgoblin of high school English teachers.