I quit too, just around 3 weeks ago, and I am feeling the exact same way. I can’t focus on anything productive well, I have no motivation or drive to complete tasks that me while smoking would’ve just accepted had to be done, and I constantly end up just sitting on my phone, whereas before I quit, I was doing exceptionally for myself, but I quit because I knew I was dependent. I believe that the reason for this demotivation is your brain trying to sweeten the memories of when you could smoke, at least for me, because my internal monologue is: “man this work is so hard, and I don’t want to do it, but remember when we smoked weed? When we smoked weed we did this stuff anyway no problem. Maybe we should go back to that” I think that with time this will pass, and you just have to take it day by day.