I'm not sure if it's normal, but I find myself visualizing bad things on a fairly regular basis. Usually it's when I'm in the car; I'll see a horrible accident that doesn't happen. But sometimes I just think about what would happen if I wasn't around anymore.
The thought of my death never used to bother me, before I was a mom. It was never one of my fears, in fact I sometimes would wish I died in a really spectacular way, like a plane crash or shark attack, rather than in my sleep or of an old age illness. But now I have to live. Someone in the world really depends on me, and if I was to die soon it could really fuck him up.