Once again I'm feeling the loss of my wasteful choices, and the disparity of being suddenly in this time that isn't mine, separated by years I didn't live, and the awareness of that much time being cut out from what I have here.
I once again feel like, having failed my attempt, there's no point in continuing it. If I am last place in a race, what's the point of making it to the finish line?
I can definitely relate, although I have learned to be a little more accepting of my past shitty decisions that are coming back to bite me now. So I'm not going to try and tell you anything invalidating (or at least not on purpose), because that annoys me when I get it. I have worked through the doubt about my existential worthiness in therapy and it was a lot.
I should have died at least a few times over by now, but my stupid body keeps disappointing me. Yet when I was finally getting off the substances I had the feeling frequently that I was living on borrowed time. Working through that and overcoming the introjection* that caused me to treat myself like a POS has allowed me to at least start entertaining the idea that I have as much right to be here as anyone else. It still surfaces frequently, but I recognize it as such and reality test it when it does... at least once it's pointed out to me that I'm beating myself up again. Not suggesting you do anything similar, but sharing what I did in case that sparks any ideas for you.
* introjection is when we (usally as children) absorb stories, descriptions, and ways of talking to ourselves that mirror what happened to us in the past based on the way we were treated.
The pithy way to describe it is, "We talk to ourselves today in the same way adults talked to us when we were growing up." It's also usually quite hostile and condemning. This leads to the often quoted tongue in cheek corollary, "If I talked to a stranger the way I talked to myself, I would be arrested."