When I experience bad stuff that is 'too much, all at the same time' a line is crossed in my mind. My mind then does something quite strange.
What happens is that my mind sort of takes photographs of things that were around while I was having the bad experience. This could capture literally anything into my memory and tie it to the bad experience.
For example, let us say that I was attacked by a gang wearing hoodies in a park across the road from Tescos. The following 'additional information' may be stored with the bad experience:
Each one of these pieces of information could act as a trigger which takes you back to the original experience. Because you feel very anxious, you may try to avoid the triggers.
If you think about it, being triggered by everyday things will make my life a misery (all the things in the list above are really ordinary, everyday things for most people). Treatment involves getting these ordinary things back into perspective and also of course finding a less restless place for the memory of the actual event.
Treatment would involve moving away from using avoidance as a strategy and towards seeing these things as 'normal' again.