I'm really confused by this comment. I know what I am now. In the grand scheme of things nothing matters, but we don't live in the grand scheme of things, we live right now.
The point of the commenter was that if we wait to have fun til later, there may not be a later. Life is about striking a balance of having fun now and sacrificing now so that you (or your family or community etc) can have fun later.
You didn't exist before you were born, so you had no idea about anything.
You "die" when you go to sleep.
So we could say most of it doesn't matter - of course if there isn't anything after our living here.