Taking your initial post and this comment into consideration, you may be in a situation I find myself in (or I may be projecting, who knows). I started out with some regular ass depression and threw in what was originally some recreational weed consumption. After a while I found myself as a daily weed smoker. My partner seems to have a much different experience as a daily smoker than I do. For me it manifests itself as you are describing, just a lack of excitement about life. I feel like my weed hangover isn’t like an alcohol one, but rather it saps my motivation to do anything productive that I’m not being held accountable for. If I was also unemployed and unable to find a job, I’m sure it would be worse for me. At the moment, I’ve cut back on my consumption and am making it a point to only partake on weedkends. Pairing that with more exercise has worked well for me in the past, but I find it difficult to get in the exercise habit with that low level of motivated energy. Finding a form of exercise where you don’t notice the work you’re doing is also helpful. I don’t much like basketball, but a friend of mine invited me out to fuck around and shoot hoops with them. Probably the easiest time I had getting in some cardio without realizing it. Nowadays, I’ve got a rowing machine that I use while I watch streaming shows. I usually find my lust for life returning when I’ve put in the maintenance on the machine that is my body. It’s a lot easier to feel alive when you feel alive.
Having just turned 43, I can tell you that I don’t think I became an adult until my early/mid 30s.