What is your worst nightmare?

I was just wondering, if any of you could share your experience.
Almost 2 years ago, I was in a really bad accident involving a drunk driver. I then expirenced my worst nightmare.
I woke up alone in a dim but white room with machinery making little beeping sounds and tubes all over the place, and I had no idea what happened or how I got there.
I started to freak out, once I realized I was in a hospital and something serious happened to me, but it was the scariest moment of my life.
It still personally haunts me, and I’m still not totally clear on what happened except for what my dad told me.