For many years, I have been looking for some form of trauma in my past that would explain my sudden mood changes, and the nervousness, anxiety, hopelessness and depression that I would feel every every once in a while. My therapist have been telling me that they are not necessarily associated with a trauma though. The following quote came at the right time and pretty much convinced me not to search anymore. Moreover, the (fictional) patient described here is quite similar to me :)
... Trauma is indeed often central in the creation of not-me; but not-me can also be outcome of much less easily observed psychic processes.
The fictional patient I just discussed, for instance, might have grown up worrying that, if he were demanding about the satisfaction of his wishes, he would have hurt or overwhelmed a parent whom he believed to be weak and emotionally inept. To demand too much from a loved person who is nevertheless perceived in this way could provoke the sense that one's own demands are hurtful enough to others to be intolerable to oneself. Such a person might come to feel, too, that his angry reaction toward the parent's perceived weakness was also not-me, since it might very well seem to the patient that the parent would be hopeless in the face of the patient's anger, resulting in guilt and shame on the patient's part. Under the right circumstances, such guilt and shame might come to seem intolerable. The patient might also worry that he would enjoy causing the parent pain, for example, and might be unable to bear the guilt provoked by the formulation of this recognition.
... the relational origins of not-me are not limited to observable, traumatic events. ---p.19, Partners in Thought