Master Fixation with Picmonic for Medicine

Fixation is an unconscious process driven by the drive to cope with emotional stress.

Fixation is a type of immature defense mchanism; Other important immature defense mechanisms are projection, displacement, splitting, dissociation, rationalization, acting out, passive-aggressiveness, and denial. Immature psychological defense mechanisms are psychological processes that play an important role in suppressing emotional awareness and increase the risk of various medical conditions. These patients are more likely to lead unhealthy lifestyles and use food and drugs to cope with external stressors.

People demonstrating fixation are partially remaining at a more childish level of development; in simple words, you could describe it as being "stuck" in an earlier developmental stage. A grown-up throwing a tantrum under stress is a good example of fixation.