I have come across this idea before.
The idea of living each day as your last.
Each day is a complete life, if you will.
Since you are already dead, Eric Greitens points it out for us:
“As usual, Seneca captured the idea clearly: “At the moment we go to sleep, let us say, in joy and gaiety: ‘I have lived. I have traveled the path which Fortune assigned to me.’ If a god gives us the next day as a bonus, let us receive it with joy . . . Whoever has said to himself ‘I have lived’ can arise each day to an unexpected gift. Hurry up and live, and consider each day as a completed life.””
The Bible says essentially the same in James 4:13-14. “Come now, you who say, “Today or tomorrow we will go to such and such a city, spend a year there, buy and sell, and make a profit”; whereas you do not know what will happen tomorrow. For what is your life? It is even a vapor that appears for a little time and then vanishes away.”
On his death, and the shortness of life, the late Jerry Weintraub had this to say:
“Until a few years ago, I was terrified of death. It occupied a lot of my time. Then my friends started to die, contemporaries, like Sydney Pollack, Bernie Brillstein, Guy McElwaine. I went to see Guy at his house, at the end, when he knew he was dying. And you know what? He was smiling. “What are you smiling at, crazy man?” I asked. “You,” he said, “because I can see that you are afraid of what’s happening to me. But I’m not afraid, so why should you be? It’s just another journey.” I thought about this again and again. It bothered me. Finally, one night, I sat down with a glass of wine and sort of interrogated myself. “What are you scared of?” I asked. “It’s the natural progression, part of the journey. Besides, you can’t get out of it. No matter how much you worry, it is going to happen. So why not just face it like you’ve tried to face everything else?” The next morning, I went out and bought a cemetery plot. I have come to terms, made peace. Not because of religion, or because of anything I’ve been told, but because I’ve lost friends and I’ve lost family. Maybe this is what happens if you live a long life. Maybe it’s the gift of survival. When more of the people who really mattered are gone than remain, the balance tilts to the next world. Your parents go, your friends go, and you realize you will go, too, and it’s okay. Death makes the rope taut—without it, we would have no stories, no meaning. I do not want to leave. I have a nice house and a nice pool and it’s a beautiful day and my cellar is filled with wine and my humidor is filled with cigars. I don’t want to go anywhere. But when God calls, I will go, and I won’t be crying.”