There is a difference between trauma and stress.  We all have jobs and situations that are upleasant but the moment those situations are over, they are over. The problem with trauma is that when the experience is over, your body continues to relive it.  Trauma is the impact that an experience has on the functining of our nervous system.  Sometimes this can be due to experiencing an adverse event or collection of events.  Trauma can also come from not just what happened but what did not happen or what should have happened, such as your basic needs not being met.   

What is traumatic for one person, may not be traumatic for another person.  It starts as something that happens to us, but eventually changes the way our brain processes information  The survival part of our brain becomes over active and signals to us that we are not safe, even when we logically know there is no danger present. 

Sometimes  this causes us to become a former shadow of ourselves.  Often we have difficulty connecting with other people, difficulty connecting with ourself, shame/negative sense of self, difficulty experiencing pleasure and joy, rage/anger, difficulty being present, and an altered sense of the world as unsafe.  When the survival part of our brain is running the show, we make choices based on fear rather than what is best for us and our lives.