Live as if Already Dead

I heard an expression: "Live as if you're already dead." It intrigued me. What does it mean to "live as if you're already dead"?
What happens when you're dead?
Nothing matters anymore. Nothing perturbs you. When you are dead, you're in eternity and there is no way to come back and fix the problems that you created when you were alive.
Why to work ourselves to death than on issues that in the long run, when we die, do not count, do not matter?
I think it is because we don't accept death. To accept our mortality is scary. So, we ignore it. Deny it. We act as if  we are going to live forever. The result ? We waste our lives on things that in the long run don't matter...
The next time you have a problem, ask yourself this question: " Will it matter when I'm gone forever? Will it matter even five years from now?"
This way of thinking might give you a tool to help you filter out what to worry and care about from what to just shrug your shoulders at—resolving to do your best, and then let go.

There is a continuation to the above expression: “Learn as if you will live forever.”
Well, true, no one lives forever but who knows when any of us will part company with this world? You might live a long life, so why not  keep learning and improving who you are. The more you know yourself, the more you can enjoy what you have or encounter.