I had the same experience. Weed is, generally, a downer so whenever I'm high all I wanna do is eat and sleep, maybe watch a movie--but I usually end up closing my eyes and falling asleep if I'm not sitting up.

The few hours after you get down from the high, though, is a different story. The next day after waking up from a night of smoking weed, I felt compelled to do my work and really felt like getting some school work done. I think it's the euphoria that comes with the weed that stays for a bit even after you've come down, not the weed itself because, as I'm sure you know, you don't really feel like getting any serious stuff done on weed.

Also, about the thinking clearly... Weed helps with that, too, I guess. Puts things in a different perspective so you can look at things from all angles. Probably where the "spirituality" that people get from weed comes from.