(setq t nil)
"Most men lead lives of quiet desperation and go to the grave with the song still in them." -Henry David Thoreau
If you care about anything you have or if you care about anything you do, then you should reexamine your life.
Here, 'care' means "to think about something as being important." Then we have the trouble of defining important. The feeling we are going for is such that if you feel a certain pride or uniqueness about something that you would almost be willing to fight for it, then you care for something. And, as we previously established (by hand waving), caring for anything is futile.
If you actually think that anything you do matters in the long run (as defined by Keynes), then you are delusional. If you think that anything you do matters in the short run, then yes, you are correct to an extent. What you do will have an impact on your immediate future, but do not place value in your current activities as being some divine proclamation that is meant to validate your existence.
You are nothing.