I am pretty sure weed has almost a reverse tolerance. I rarely smoke these days, as I need to pass drug tests at work, but I used to be a multiple time per day smoker, and smoked hash at least one time per day. I learned very quickly that the more you smoke, the less you need. Towards the end of my use I actually stopped using concentrates, and just bought a tiny little one hitter than looked like a cigarette. The tiniest pinch, like you, not even half of .1 would have me high for a few hours. Any more and I would either get really paranoid and anxious and need to take .5 of xanax before panic attack, or I'd get insane couch lock, and not even want to move for the next 6 hours.
I completely feel you. I like my highs to be productive. If they cant be productive, I at least like to play video games or clean the house, or go for a run. At least so I feel like I'm doing SOMETHING besides sleeping and eating and sitting on the couch watching tv all day. I've found that if I smoked a tiny tiny pinch, the high could be productive, and burnout wouldn't happen. Any more, and I'd burnout the high would turn to a stone, and I wouldn't do shit all day.
You are probably smoking some pretty potent bud, because I noticed that with mids and brick, I could smoke all day every day and not feel lazy. It was when I moved to nug, and hydro being all I smoked that I eventually became stoned far too quickly.
I've also read that similar to opioids, if you use your cannabinoid system too much, your body will downregulate them, and make less receptors available. Where with an opiate you would take more to counteract tolerance and get higher, weed has a pleateau. Meaning that one tiny hit would be all you need. I see so many people take huge ass hits then lay around all day, or fall asleep an hour in, and be typical lazy stoners. I liked to defy the stereotype of lazy stoner and get shit done, and tiny hits would allow me to do that.
May I ask, are you looking to use cannabis for sleep, or to unwind after a long day, or are you using it like me to be creative, productive, and get stuff done?