CCC 1007 Death is the end of earthly life. Our lives are measured by time, in the course of which we change, grow old and, as with all living beings on earth, death seems like the normal end of life. That aspect of death lends urgency to our lives: remembering our mortality helps us realize that we have only a limited time in which to bring our lives to fulfillment:
Remember also your Creator in the days of your youth,. .. before the dust returns to the earth as it was, and the spirit returns to God who gave it.1

1 Eccl 12:1,7.