Depression can hit this way, too. You can be apathetic towards everything, no motivation, stuck in your head. It can be easy to get caught in a downward spiral, trapped in the vortex of negativity you no longer feel in control of.
The apathy is probably the worst part. Like, I know this thing I need to do is important and that not doing it will have some very negative consequences, but I just don't care enough to do it. Then, last-minute panic sets in and I half-ass it, which is still good enough, but it hurts that I could do so much more if my brain wasn't malfunctioning like that.
This is why I like weed. It's not so much the body feel (though that is a nice bonus), as much as it quiets my mind and allows me to have some fucking peace and quiet in my own head.