We all, to some extent, base our self-identities on certain aspects of our circumstances: job, family, place, appearance, etc. These are some of the components of who we think we are, though some people rely more heavily on these externals for their identities than do others.
When there are shifts in any of these circumstantial factors, as will inevitably happen, it strikes at our core and seems to threaten our own solidity. For people who are heavily self-invested in circumstances, change is an existential threat, and profoundly disturbing.