Immortality
When does a person die? When that person is forgotten. When any information about that person as an individual is lost. You lose your grip on this universe when you are forgotten.
The Unknown Soldier is remembered. The unknown soldier is no one in particular. But the individual is lost forever. We mourn the fact that this anonymous person gave his live to ensure our future, but we have not remembered him. The unknown soldier is an artefact of the past, when we were not able to be absolutely certain of a body's identity. Now we have DNA testing and other ways to identify a body. We also keep diligent records of who went into conflict. And those who did not emerge can be positively identified.
How can we solve this problem? By tracking our genealogy. Our turning points. We owe it to those who came before us and ensured that we would be where we are now. Let us not forget them. Every time a person's identity quietly slips away from the memory of the last person to remember them, a person dies. Really dies.
How can you be remembered? You can be remembered like Adolf Hitler is remembered today. Or you can be remembered like Albert Einstein. Being remembered as Adolf Hitler is a fate worse than death. Do your best to improve yourself and your relationships with others. Do your best to educate, discover, share. And people will remember you. And your hold on this universe will be firm.