The roots of our identity and sense of self are found in our:

   Childhood

Explanation:  Everyone realizes their identity and begins to feel the self in their earliest childhood. The first information we have about ourselves is to feel our self, creating a sense of ourselves, which is a sense of personal identity. This begins to manifest itself in childhood when the attributes of the self occur, for example, the child feels that can walk, eat, run, laugh, etc. Later these attributes become more complex and create a certain behavior. What attributes a child will adopt as important to him, and what determines his/her behavior depends on what the child is witnessing during childhood, the parent, the environment, what the child is hearing from others, etc. All these attributes the child adopts by sense, become an integral part of the identity, i.e. they are upgraded into the existing sense of self and determine the behavior.

glass wants to live in a world of super heroes and villains. he have lived all his life trying to be responsible for the creating the origin story of a super hero; he schemed and caused many incidents (many of them fatal) hoping that someday someone with superpowers would show up and save the day.

he knew himself very much. he saw himself as a villain of a real-life super hero story. he was aware of his strengths (more than smart enough for being manipulative and scheming) and weaknesses (having fragile bones and having to rely on his mind to succeed).