I had a moment when I was around 25... I was very active, but I was noticing that I was starting to heal and recover more slowly than I did when I was 19. Then it hit me, this is basically just going to get worse and worse over the decades, and then I'm going to die.

It helped, I kept being like "wtf is wrong with me" but actually, no, I was just noticing the first little tiny signs of aging.

Now the trajectory has kept up, and I have to squint to read things that I could once read easily. Both my parents used reading glasses, and in 5 years I'm going to need them myself.