Weed. Had to quit for an extended family holiday. I've had t-breaks like that a dozen times or so over the past 20 years, but was otherwise smoking daily. When I got home last September, I smoked a couple of bowls I had left behind and then just... stopped.
I don't really have much to say about it. I don't feel significantly clearer-headed or motivated. No profound physiological impact. Same as when I took breaks from it, had super weird and vivid dreams for a short while after stopping.
I'll partake when I'm offered a doobie at a party, but I probably won't go back to my old habits.
I think the reason I stopped is because I started taking (non-stimulant) ADHD meds a couple years back and the increase in dopamine made me just not feel like it anymore.
It would previous help me to regulate my appetite, helping with my comorbid binge eating disorder. I could get dopamine from smoking weed that I'd otherwise get from food. Of course, I'd usually get it from both, but having a good time stoned was definitely a fun thing for me that'd reduce my general cravings for other stimulation. But the meds are more effective (and specifically kill appetite as a side effect)