Burnout is a psychological term for the experience of long-term exhaustion and diminished interest. Research indicates general practitioners have the highest proportion of burnout cases (according to a recent Dutch study in Psychological Reports, no less than 40% of these experienced high levels of burnout). Burnout is not a recognized disorder in the DSM although it is recognized in the ICD-10.
The most well-studied measurement of burnout in the literature is the Maslach Burnout Inventory. Maslach and her colleague Jackson first identified the construct "burnout" in the 1970s, and developed a measure that weighs the effects of emotional exhaustion and reduced sense of personal accomplishment. This indicator has become the standard tool for measuring burnout in research on the syndrome. The Maslach Burnout Inventory uses a three dimensional description of exhaustion, cynicism and inefficacy. Some researchers and practitioners have argued for an “exhaustion only” model that sees that symptom as the hallmark of burnout. 
Maslach and her colleague, Michael Leiter, defined the antithesis of burnout as engagement. Engagement is characterized by energy, involvement and efficacy, the opposites of exhaustion, cynicism and inefficacy.
Many theories of burnout include negative outcomes related to burnout, including job function (performance, output, etc.); health related outcomes (increases in stress hormones, coronary heart disease, circulatory issues), and mental health problems (depression, etc.).
Although burnout is work-related, most responsibility for burnout currently rests on the individual worker in the United States, as well as the individual company, as it is in a company's best interest to ensure burnout doesn't occur. Other countries, especially in Europe, have included work stress and burnout in occupational health and safety standards, and hold organizations (at least partly) responsible for preventing and treating burnout.
Psychologists Herbert Freudenberger and Gail North have theorized that the burnout process can be divided into 12 phases, which are not necessarily followed sequentially:
* A compulsion to prove oneself
* Working harder
* Neglecting one's own needs
* Displacement of conflicts (the person does not realize the root cause of the distress)
* Revision of values (friends or hobbies are completely dismissed)
* Denial of emerging problems (cynicism and aggression become apparent)
* Withdrawal (reducing social contacts to a minimum, becoming walled off; alcohol or other substance abuse may occur)
* Behavioral changes become obvious to others
* Inner emptiness
* Burnout syndrome
p/s: I just got burn out..