Some folks apparently consider this depressing, but I found it helpful to accept that I'm just a pile of atoms drifting through the universe.

I'm 'alive' in the medical sense, so there's lightnings going between the piles of atoms within my brain and another pile of atoms continues to wobble in the appropriate way to pump a soup of atoms.

But I'm not alive in a sense that inflates meaning into it, which we do a lot:

• the completely religious ideas, like heaven/hell or being reborn (in a sense that isn't just parts of your pile of atoms being reused in other living piles of atoms)
• the widely accepted but undefined 'souls'
• some elevated meaning of 'consciousness' (which does not just mean your pile of atoms has some concept for recognizing piles of atoms as individual objects)

Similarly, the past and the future don't exist. They're concepts we've made up. The whole time traveling brouhaha in science fiction might make one think that they exist more concretely, but that nonsense foots on a missinterpretation of Einstein's theories.

So, there's not a meaning to your past self being alive or not. It really is as simple as it just not existing.

And ultimately, without inflating the meaning of being alive, there's nothing to be sad about either. Because, while it's fancy when piles of atoms do the lightnings and the wobbles, it doesn't matter which concrete atoms are part of that fancy pile.

You can even stop thinking about your pile of atoms and rather consider yourself part of the big pile of atoms which is the Earth or the whole universe. That big pile of atoms is quite immortal.