Depersonalization is a core symptom of burnout but is also seen in depression as well in other mental disorders.
Depersonalization can consist of a detachment within the self, regarding one’s mind or body, or being a detached observer of oneself .
People feel they have changed and that the world has become vague, dreamlike, less real, lacking in significance or being outside reality while looking in.
It is the strangest feeling. I remember seeing people through the window and asking myself ‘why’? Why do they move? Why are they happy? Why does this all happen? I could see people but I could not reach them, I couldn’t open myself up to make a connection with someone or something outside me.
‘Inside me’ wasn’t better. There were some vague ‘feelings’ but the mind had no connection to the body. I tried to do yoga but I was going through the motions. It’s like eating when you have a severe cold and everything tastes bland. I was some kind of bland.
In this post I’ll write about depersonalization as a more temporary or acute symptom and not about chronic depersonalization which refers to depersonalization-derealization disorder, which is classified by the DSM-5 as a dissociative disorder.
Degrees of depersonalization and derealization can happen to anyone who is subject to temporary anxiety or stress. Depersonalization can occur with the following mental illnesses: borderline personality disorder, anxiety disorders, clinical depression, bipolar disorder, schizophrenia, schizoid personality disorder, OCD, migraines and with sleep deprivation.
What is it exactly?
Individuals who experience depersonalization feel divorced from their own personal self by sensing their body sensations, feelings, emotions, behaviors etc. as not belonging to the same person or identity. Often a person who has experienced depersonalization claims that things seem unreal or hazy. It is quite difficult to explain but I felt something, it was like someone else felt it and gave me the ‘mental note’. It is like living through a movie. You see things outside and you know you are to react to that. You don’t feel how to react, you think how to feel. There is no connection, you need to take some questionable bridges because the highway of feelings is ‘under construction’ in the best case, totally out of order in most cases.
Depersonalization is a subjective experience of unreality in one’s self, while derealization is unreality of the outside world. Although most authors currently regard depersonalization (self) and derealization (surroundings) as independent constructs, many do not want to separate derealization from depersonalization. With me they occurred both at the same time, which can be confusing to say the least.
I am crazy for feeling that way?
Not really, depersonalization is the third most common psychological symptom, after feelings of anxiety and feelings of depression.
Why would your mind react in such a way?
Psychologically depersonalization can, just like dissociation in general, be considered a type of coping mechanism. Depersonalization is in that case unconsciously used to decrease the intensity of unpleasant experience, whether that is something as mild as stress or something as severe as chronically high anxiety and post-traumatic stress disorder. Depersonalization is an overgeneralized reaction in that it doesn’t diminish just the unpleasant experience, but more or less all experience – leading to a feeling of being detached from the world and experiencing it in a more bland way. 
Resources and more information.
 Sierra, M.; Berrios, G. E. (2001). “The phenomenological stability of depersonalization: Comparing the old with the new”. The Journal of Nervous and Mental Disease. 189 (9): 629–36.
 Cardeña, Etzel (1994). “The Domain of Dissociation”. In Lynn, Steven J.; Rhue, Judith W. (eds.). Dissociation: Clinical and theoretical perspectives. New York: Guilford Press. pp. 15–31.
Article on Wikipedia ‘Depersonalization‘.