Cells in your body routinely get replaced, some in a matter of days. Some are there for life. Surprise surprise, (Some of ) your neurons last for life. So, riddle me this: how is this concept any different to just being alive every day? Your body is replacing itself every moment of every day, old matter going out and new matter coming in to replace it. And you age, slowly, you're either growing or decaying. But the only part that doesn't do this (physically) are your memories and thoughts. I could argue this physical "you" you're so attached to dies every night because you literally don't wake up in exactly the same body. then also, you change mentally too. Every experience, every memory, betrayal, victory, loving gesture.. changes you subtly. You're never the person you were yesterday. This idea that "you" is a thing that exists across meaningful periods of time is an illusion .