When you’re born, you have no sense of identity. You’re a loose collection of ego states that are organized by needs, like the need for food, the desire for attachment/love, and so on.
As your brain develops, by around age 6 these ego states will merge to form a singular identity. Your memories and experiences inform your opinions and preferences. Children should develop a cohesive sense of self with an autobiographical memory that follows a consistent narrative. They have a sense of their place and role in the world, and the relative stability and safety of the things within it.
On the other hand, if you are exposed to trauma, you may have learned to dissociate as a survival mechanism. Your brain simply could not acknowledge the nature of whatever was happening. Often, it can’t resolve the fact that a person who supplies food and shelter is also a person who causes harm and betrays trust. Ego states never integrate, and instead grow in pieces, often isolated from each others awareness and memories. In order to survive, you adapted and grew to be the way you are now.
If you have DID you’ve been multiple since childhood. If the diagnosis is new, don’t be scared. Your parts have always been there and you’re alive now, right? Every part of you deserves to be heard and welcomed in from the dark, and they deserve empathy and comfort, even those that may scare you right now.
You’re all in this big bad world together, and you’ll succeed or fail as a team.