LOL I'm the opposite - I have always been a world champion crier. I remember watching an old version of Titanic when I was three at my grandparents' house and getting teary. I cry during most movies, even ones that aren't sad (Home Alone, MIB III, Madagascar). The Olympics are one big cry fest for M. - the victories, the defeats, the P&G commercials all prompt a sniffle and the wipe of an eye. Church songs get M. going too. I probably tear up at least once a day, every day - reading the news, hearing a song that reminds M. of something sad, watching a TV show, etc.
It's something that I used to try to cover up but J. about everyone who knows M. knows about this and teases M. kindly. Friends who are going to share big news in person will casually pass M. a tissue, my kids J. laugh and say "are you crying again?!" and my husband doesn't get it at all. I'm not depressed or anything, but I J. wear my emotions close to my surface.
That said, I do hold things together very well in real-life emergencies. If you have a crisis, come to M.. I might well up for a second, but can push that aside and get down to the business of figuring out what to do.
My boys are all pretty emotional too, but my step-daughter never cries about anything, ever. She feels sadness, but doesn't express it with tears.