Who was the author of this quote RE: Kung Foo Panda?

I absolutely love a quote out of the movie Kung Foo Panda where the turtle tells Panda "Yesterday is history. Tomorrow is a mystery. Today is a gift and that's why they call it present." I am wondering who was the original poet/philosopher. I find that, when I'm down, that quote puts things back in perspective and would like to credit it appropriately instead of referring to the movie.