I think what would cause me to cry is the purity of my emotions at the time. It's like overdosing on a drug because it's too pure and strong. For example, not too long ago a friend of mine died, and while I was thinking about that, and nothing else, I could sense that I was about to cry. It was because I was lost in a world of fantasy and emotion.
I was thinking about things that I would never otherwise think about. I was being sentimental about things that I'm not usually sentimental about. I was imagining myself having a very emotional reaction because that's usually what happens to people when someone close dies. While I was thinking about all of these really sappy things, I kind of realized that I was only doing it to see what it was like. It didn't really resonate with reality to me. I was about to get all emotional and cry about a deep sadness that I was merely imagining in my head.
And I think that's why I don't cry that often. It seems fake to me. I wonder, though, if that feeling that I get sometimes is what it's always like for other people who cry easily. To get lost in an emotion as if it's actually reality... and instead of realizing it's not and snapping back, going even deeper into it. It would be easy to cry if I did that, and I'm not really opposed to it so I can seem tough, it's just that it doesn't seem to make sense to do it. I like having my usual perspective on things. I take on the emotions slowly, one bit at a time, processing them as I go with my analytical mind, sort of like building up tolerance to the drug so I don't overdose on it. And that's just my natural way of doing it, I guess. It wasn't even a conscious choice I made because emotions scare me or anything. It's just a system I adopted over time. I got better at cleaning dishes and dealing with negative emotions.
There's some people, where if you call them a bad name, they will cry. I've never understood that. It's like they are instantly transported into a different world or something. They are transported into a world where the name caller's opinion is actually important, or into a world where they hate themselves. They do that instead of taking a step back, analyzing it for a second, and concluding that the other person is a jackass and that there's nothing to worry about. If you're going to get lost in fantasy land, at least have it be a land where you're the shit so you can fight back!
So, my made up on the spot theory is that people cry when they leave the big objective picture behind and enter into a fantasy where their emotions are allowed to run freely. In other words, they overdose because it's too powerful to take straight. (And I'm not implying that it's actually a bad thing, that's just how it happens. My analogy is not perfect, because overdosing on drugs or something IS usually a bad thing, but you know what I mean. At least I hope so.)
Gratitude and happiness are subject to this too, I believe. Only sticking with the cold hard facts doesn't always make things better. How could we love without imagination?