I've known my triggers since childhood and am usually very careful to structure my life to avoid them. In my family, migranes are heredetary on my father's side. My grandma, my brother, and several of my cousins suffer from them.
Take today for example. There's a series of thunderstorms moving in, but they're coming gradually, so the chance of a migrane is slim to none, but my back is causing me considerable pain. I can't even sit comfortably. (I have an old back injury; when the weather changes, my back and the 2 bad knees certainly let me know.)
The back pain is annoying, but I know there are some stretching exercises I can do do ease it, and a hot bath will do me wonders tonight, so no painkillers. (Despite this being at the level I'd normally take a painkiller for.)
I've had headaches from dehydration, from tension, and from low blood sugar.
However, a Migrane ...
A Migrane is to those headaches as flying the concorde is to riding a bicycle. I lose my vison. Light, sound, and smells cause spikes of intense pain. I lose muscular coordination. I become very dizzy. I lose feeling in parts of my body. I vomit.
They last 6-8 hours. Plus a day to recover.
The pain is so bad I've contemplated crawling to the toolbox and grabbing a hammer.
I only thank god I don't have more than 4 or 5 a year.
If you have access to a local library, there's a really good article in the March 2000 Discover Magazine about what exactly goes on in the brain during a Migraine.