The idea that personal identity might not exist continues to strike me. How can I identify that I am the person who I am? How can I know that I am the same person as my ten-year-old self?
Ordinary people rely on memory, but you cannot remember everything. Only a few important moments are clear; most of the rest is vague. If we accept that memory can verify our identity with our past self, then memory would need to be continuous. But it is not. You can only identify yourself in certain moments that you remember now. For almost eighty percent of your life, you cannot be sure that was you. As Hume said, when we try to find the "self," we find nothing but a bundle of chaotic sensations, it is not successive.
Another perspective appeals to the same body. Yet biology reveals that every seven years, nearly all our cells are replaced through metabolism. That means you do not actually share the same body with your past self.
If my deduction is correct, we are forced to accept a shocking and terrifying fact: We can only exist in the present. The person from the last second is not me, nor is the person of the next second. However, this is, after all, an extreme conclusion. But it also reminds us that everything you have done risks becoming meaningless if you forget it—because then it would belong to someone else.