I could be blinded or crippled in an automobile accident. A tornado could wipe out our neighborhood or my old hometown. If I insist on defining myself to myself by a tangible but transient trait, I run the risk of becoming nobody in the blink of an eye. I turn my identity over to that which is not only beyond my control, but not inclined towards benevolence on my behalf. Once again, I find myself in a position of moving on to new pursuits and relationships, untangling myself from the activities and associations that had come to identify me.
Transitions are unnerving.
Change is frightening from the inside, and often perceived as betrayal by the others in one's life. There is the converse, too, though. What I perceive as a major defining factor, a significant part of who I am, may be viewed as peripheral by others. They may not understand why cutting a particular tie might seem so traumatic. This is particularly true of those who were not aware of the existence of that association or tie to begin with.