I have them so often that I'm used to them. I'll be going along, having a nice day, when suddenly I'll get a graphic vision of one of my kids being killed by a truck or me drowning myself in a certain lake near my house. I have lots of other ones but these two are the most common. I've learned to tell myself that my brain is lying to me and that I'm OK. I also visualize a big STOP sign and tell myself to do exactly that. It works more often than not.