In parts therapy today, this was my realization. The more trauma in your history, the more complicated personality you have in the present.
On the extreme end of the “inner personality parts” spectrum, those with Dissociative Identity Disorder (multiple personalities) typically have a higher amount of trauma in their history than the average person.
Where does this leave us?
I don’t know. You could ask how this applies to you. Do you have trauma in your background? if so, can you imagine how that trauma may have created inner complications? Irrational fears, anger, and so forth.