It's like a concrete (fortified) imagination of something bad happening I think.
I think that it's phobia related with me. With me it's also obsession that I try to dismiss. Sometimes I can do something that I like in a hobbie,and get my mind off of it.

Sometimes I can't get my mind off of it,and I have to let it fade away,while getting clobbered with other thoughts that I have to let fade away also.
I sometimes write them down. Sometimes they are false guilt burdens(This is my own terminology),then I'll get another one.

These things are very complicated,and feel real. When it first begun,it was as if a black cloud was moving over me. Horrible. This is where emotionally normal people stop comprehending what I am saying. BF