I too have vasovagal. I would get horrible abdominal cramps and go to the bathroom. Then this overwhelming wave of heat and lightheadedness and sweating and feeling of not getting enough air would come over me. I would feel like I was gonna passout and fall over. The only thing I can do to try to stay clear as possible is to run cold water in the sink next to me and keep my hand under it. For some reason the cold water on my hand helps me stay more lucid and focused. (Even though you don't feel lucid or focused.) And breathe as well as you can.
It is so embarrassing because you HOPE you don't need help one day because of it and you are on the toilet. Sometimes it feels as though you are going to die because you have no control over what is happening. And you think "Please no. Not like this. Not on the toilet. I don't want to be found like this."

I don't know if it is related but I used to pass out during the plasma donation process. When they would take the blood out and seperate it I was fine, but when they would pump the blood and saline back in I would pass out. After two times the assistant said she didn't think I should try for a third. ( I would feel the cold saline shooting through my veins then I would start to go out. Maybe the cold of the saline lowered my heartrate and made me pass out. Or maybe the dilution caused hyponutremia or something.)