Compartmentalization is an unconscious psychological defense mechanism used to avoid cognitive dissonance, or the mental discomfort and anxiety caused by a person having conflicting values, cognitions, emotions, beliefs, etc. within themselves. Compartmentalization allows these conflicting ideas to co-exist by inhibiting direct or explicit acknowledgement and interaction between separate compartmentalized self states.
According to Glen O. Gabbard, often ‘people with a borderline level of organization… have to compartmentalize people into “all good” and “all bad”’, on the principle that ‘compartmentalizing experiences… prevents conflict stemming from the incompatibility of the two polarized aspects of self or other’. Often, ‘when the individual is confronted with the contradictions in behavior, thought, or affect, he/she regards the differences with bland denial or indifference’.