And, also, some people are not able to remember certain aspects of the trauma. People suffering from PTSD often show markedly diminished interest in significant activities, feelings of detachment, their emotional range is constricted, and many people show a sense as if their future is foreshortened. Then the last cluster of features of PTSD has to do with physiology and that relates to increased arousal. Also, in this aspect of increased arousal, some people have outbursts of anger and irritability. Other people have difficulty concentrating and they can be hyper-vigilant and their friends and family may notice they have exaggerated startle response.
Some people have an immediate reaction and it resolves within three months.
Much more common is a chronic subtype where the symptoms last more than three months. In fact, sometimes the symptoms of PTSD get worse over time. They can, indeed, last a lifetime. 20 or 30 or more years. There are concurrent disorders of the mind and psyche that tend to get loaded on, like depression and the consequences of self-medication through alcohol and substance abuse or the loss of family and friends.