Like this situation above, with friend #2. She said some things and I felt hurt/uncomfortable, didn't react immediately, but then she said some more things (with her vehement tone of voice) and I started crying. Then she got upset with me and I got even more upset.
She didn't do this on purpose, so why did I get so upset?

Or when I was at school, teaching, and I cried in the classroom cause they (two or three high school kids) were being rude and disrespectful or even threatening to me. And I was under a lot of external stress then (Granny had cancer, parents were retiring and stressed about money...)

I'd especially like to stop the 'crying' mechanism whenever I feel 'in danger' or threatened. (And under a lot of stress.) I know it probably stems from my father, he could be rude and crossing boundaries too, but usually stopped when I cried.
I've cried at good things too, sometimes, when touched or moved...
Once it may have even saved my life when I was attacked.

It would be better if I didn't cry in such 'innocent'/job-related situations and would just calmly express my sentiments that I do not like that kind of behaviour, that I expect them to apologize (when appropriate) and behave better...

That's sort of what I can come up with right now.
I've looked into the sweets/gluten sensitivity and there might be some connection, got my episode of psychosis/schizophrenia when I was living gluten-free, and don't currently dare to go gluten-free again.
(I once had a crying spell in an inappropriate situation when it was about something I held important and I ate some bread when I was gluten-free, or when I drank some very sweet juice... It might or might not be related.)

A bit afraid I'd cry or 'overreact' in a job/career-related situation again (when I would have one). Might need to start another thread about that though