do you know your triggers?

I was diagnosed 10 years ago, but it is only the last two years that I have been an invalid. when people refer to triggers, I am confused. I have not been able to I identify triggers. I might have some really good days and out of the blue I feel awful. I am never able to figure out the reason. some times there is a day when according to the weatherman I should feel awful and I feel great. any thoughts?