One of the consequences of trauma can be the development of Posttraumatic Stress Disorder (PTSD), which has been claimed to be the most disabling of all psychological problems. When a trauma has been very severe and complex people often develop dissociative responses, such as a sense of detachment from the body or a sense of things feeling not quite right or unreal (derealisation). Dissociation can happen with or without the development of PTSD. Some trauma has been so severe, especially when it happened in childhood and few resources were available to the person at the time, that the traumatic events may be dissociated and the person remembers only fragments or very little of what happened to them. Sometimes, people had to develop different parts or personalities to enable them to survive the traumatic events. This can result in various dissociative problems, including Dissociative Identity Disorder (DID). At the time when the trauma happened dissociation was an automatic and adaptive response, but now it may be highly disabling.
Even if you feel well on the way to overcoming your traumatic experiences or losses, an upcoming 'anniversary' of the event can have an unsettling effect.