Absence and Loss

Was eating my breakfast and thinking of Narcissism in Freud and Klein and the actual death of the mother when it occured to me that besides psychoanalytical side of the fact each individual then becomes the loneliest creature. When one's parents are gone and s/he thinks her/is roots are lost or the ones causing her/is existence are extinct, what kind of emotional aura falls round the ego that culminates in mourning/melancholia/mania, and what factors decide which way to take?