Why do I have the same nightmare over and over again?

This really has been eating me up on the inside. I stopped talking to my close friends about it. I feel like it’s pointless because whatever they end up saying, I will still end up having the same nightmare. I even went to see a therapist about it but that didn’t help too.

Three years back, I had a car accident and till this day, my nightmare involves a vivid flashback of what happened on that night. I don’t have the nightmare everyday, but at least twice a week. It is horrifyingly realistic and very disturbing because I experience that night over and over and again. It fucks up my sleeping patterns and I end up not sleeping the whole night. I was just wondering if anyone has an idea as to why this is happening.

Have you ever had reoccurring nightmares? How did you deal with it?