Social exclusion, or ostracism, is being excluded or rejected by others. It is the common behaviour within social situations. Detecting social exclusion could be essential for the survival of human creatures, as social exclusion could threaten the basic needs of human creatures: self-esteem and feelings of belongingness. Williams temporal need threat model introduces how individuals react toward ostracism. Usually, individuals can recover from social exclusion quickly by behaving pro-socially to reconnect to others and fortify the basic need(s) threatened by social exclusion. However, for individuals with higher social anxiety or social anxiety disorder, the negative social belief about themselves (unpopular, shyness) within a social situation inhibits their recovery speed from exclusion and desire to reconnect to others. When social exclusion happens, individuals with higher social anxiety or social anxiety disorder become more vulnerable in social situations. Individuals lose their ability to get used to social situations when they suffer long-term social exclusion. Acceptance and Commitment Therapy is suggested to be a helpful therapy for individuals suffering from long-term social exclusion and social anxiety disorder.