These Dreams...another one.

I had a dream that i witnessed a car accident and the man inside was trapped and couldnt escape. The car was leaking oil and he was screaming "i have to get out of here before the car blows up." I just stood there dumbstruck, and sure enough the car blew up right before my eyes. I saw the man catch on fire and scream and i didnt do anything about. Everything was so real, i even remember the car, it was a deep blue sedan. Why do i continue to dream these unpleasant dreams?