The recognition that there is a beginning and an end means that you can do what you want with the time you have here. I have seen this idea described as “the dash,” the little mark between the day of your birth and the day of your departure. You get to decide what you do with your “dash.”
You are free from having to worry about all the inconsequential things that happen from day-to-day, as they are meaningless in the big scheme of things. Nor do you have to consider what other people think about you, since almost none of them will be standing up to provide the eulogy Covey recommends you write as a way to live in line with your values.