We are kept in this great interspace and are constantly held in the center of it for one reason only: to grant us free choice in spiritual matters. The equilibrium in question is spiritual, because it is an equilibrium between heaven and hell, and therefore between good and evil. All the people who are in that great interspace are inwardly in partnership either with angels in heaven or with devils in hell. (Today that partnership is either with Michael’s angels or with the dragon’s angels.)
All people after death travel toward their own kind in that interspace and associate with people who love similar things. This happens because love connects all individuals there with others like themselves and allows them to breathe freely and to be in the state of life they were in before. Then step by step they shed outer traits that are not in harmony with what is inside them. Once that process is complete, good people are lifted into heaven and evil people move to hell. In either case they gravitate toward people with the same dominant love as their own.
from True Christianity, Section 477