It's taken me quite a while to figure this one out, but after a long, long session of crying today (for really quite trivial reasons, like phone bills, maths results and being yelled at by my mother), I figured out why I cry.
I'm not sure about most other people, but I don't cry when I'm sad, nor do I cry "with joy". I don't cry often, but when I do, I cry with guilt. It's actually rather annoying when people think that I cry because I think I've been done wrong. Mmm, I like to think I'm deeper than that.
For example, ever since school started again, I've been excessively tired (hence the lack of posting), and that has made me a little bit irritable, especially towards the little motherly things that mothers do that make you feel somewhat smothered when you most want to feel independent. I can acknowledge, then, that my attitude has been rather horrible/dismissive towards my mother, which I think is wrong by all means. She yelled at me for a while about that issue, and besides having a pet hate of being told what I already know, I felt an overwhelming guilt for treating her so poorly.
So I cried, and when I cry, I cry for a long time and it's because of guilt. Guilt isn't something that just goes away after crying a little bit, so I'll cry more, continuing my feelings of guilt. Obviously, the guilt never really goes away but eventually I feel better for being such a shitty person.
She yelled at me a little bit more because she assumed that I was being unappreciative, and that "no matter how many times she would tell me, I couldn't understand where she was coming from." Obviously, I did, and I'd understood since long before I began doing it, but despite that I continued being annoyed at her for misunderstanding me. Vicious cycle.
As for the phone bill, I just felt really bad for having somebody else pay it for me while I remain unemployed. As for the maths results, I felt guilty for having truly studied, freaking out when I knew how to do everything required of me, and did poorly. I did myself wrong there, but that doesn't stop me feeling guilty for not having done better.
You're probably thinking, what a cold-hearted sop. Sorry that I don't cry for the same reasons as you must.