I feel like I'm at an upward trajectory at the moment. I'm also NEET but as of now intentionally and also traveling. I meditate every day (pranayama, vipassana, zen), I work out every day, I do yoga every day, I eat healthy every day, I don't do drugs except for alcohol and that in moderation, I stopped watching porn more than a month ago, I stopped picking the skin on my nail beds finally also about a month ago, I do my best to learn what is good for me and what is harmful and then I do my best to do more of what's good and less of what's bad. Suicidal ideation - yes - but also almost gone for a while now. My convenient situation - traveling - having all the time for those things and being able to avoid the daily ordeal of working - will end in about two months. I hope I'll be able to integrate all or some of it back into "regular" life. But if I don't - I feel like I can basically copy paste your text to the T in a few years - when I myself will be in my 40s.

But what I can give you as advice is to break away from this idea that the "best part" of your life is over and you need to "salvage" something. Living happy is always about being present in the present. Age does not matter from that perspective! And you also seem like somebody who is detached from your spiritual needs - I think that's where you have to start looking. There are many inspirational interviews and talks to be found online by Eckhart Tolle, Gabor Mate and so on.