I've never heard ANYBODY say that weed gives them motivation to get shit done. wtf?
It's hard to explain, but here's what it feels like.
When sober, my mind is foggy and I don't have a clear sense of direction of what needs to be done. When I get high, everything in my mind clears up and I'm allowed to focus on one thing at a time. I'm also allowed to look at things from a 3rd person perspective, so if I get high I look at the big picture of what needs to be done, and then I proceed to do one thing at a time.
Of course, if I get too high, then my cognitive abilities are completely ruined and all I do is sit on a couch and watch TV. You gotta hit that sweet spot (few hits from a vape).
Another problem is the weed strain. Some weed strains work much better than others, but the ONLY way to find which strain works best for you is via trial and error.
One last thing needs to be said. I don't get motivated every single time i get baked. The moments of inspiration are completely random, but when they do happen, it's awesome.
Carl Sagan is an excellent example of a figure who got baked to further his intellectual and professional pursuits.