I end up doing that all the time when I zone out, while falling asleep, in the shower, etc. Often I get so into it I'll make myself cry. I never really thought I dissociated before, just minor zone outs, but is this a form of it? 

For example, I imagine my sister dying. Or me getting in a car accident. Or my (now ex but at the time) boyfriend breaking up with me. I'd imagine it in vivid detail and I couldn't make myself stop. 