Don't let anyone tell you what that trauma might be, it is for you to figure out if that is actually what it is. As you explore your mind and your skills, the memories will unveil. Having someone you love and completely trust when they do appear can be very helpful. But in situations that lack the love and trust, you have to depend on yourself. Self love and acceptance is necessary anyway.
Traumas can often be major triggers for psychic potential.
You've probably heard stories of women lifting cars off of their children in crashes, or of autistic children having a genius talent in music or numbers, etc. Some Witches feel detached from mundane life, maybe because they walk frequently between the worlds. Many psychics also report a sense of isolation, of being an observer, or of having to distance yourself in many situations. Again, this is frequently a natural safety mechanism, like the lack of memories above. These things probably don't happen to millions of people, but they do happen to many.