I do it as well.
For me, it has nothing to do with the feelings, I don't think, it just seems to happen automatically with strong doses.
It's not like normal crying, I'll just have tears in my eyes or them slowly dripping down my cheek as opposed to pouring out when I see or feel something incredible, beautiful or horrible. And it'll last for a long time, regardless of how the things I'm experiencing are changing. From what I can remember, having eaten a quarter to a half ounce and having my memory of events somewhat distorted, if I lay with my head on one side, the other eye would end up way too dry; like I'd been keeping them open for too long without blinking, staring off with the million mile gaze and five mile smile for too long.
I do something similar with pills; which seems contradictory to what I should be doing. Quite often I'll start continually yawning as they go into my bloodstream, regardless of how not tired I am I can't stop doing it. Then the yawning will suddenly disappear as they start picking up; the same way the sick feeling for both pills and mushrooms seems to vanish at a certain point after eating them.
I think they may be some of the less well documented side effects of the drugs. They're affecting your nervous system at a high level, and your nervous system controls things like your tear ducts and urge to yawn at a subconscious level; which is often connected to the CNS in some way to report back between the two. It would be narrow minded to be distorting your CNS at such a high level and not expect those effects to propagate down to the peripheral nervous systems. You can see the subconscious, peripheral effects all over a pill chewers face, huge pupils and a muscle tension that looks like it's trying to compress coal into diamonds. Trippers are the same, with their gazing off into the distance and grinning, or scrambled speech.
"The walls are like jelly peas with coats made of apricots!"
"WHAT?!"
