As the nervous system matures, a baby reclaims some regulatory processes and performs them autonomously. Even after a peak parenting experience, children never transition to a fully self-tuning physiology. Adults remain social animals; they continue to require of source of stabilization outside themselves. That open-loop design means that in some important ways, people cannot be stable on their own—not should or shouldn’t be, but can’t be. This prospect is disconcerting to many, especially in a society that prizes individuality as ours does. Total self-sufficiency turns out to be a daydream whose bubble is burst by the sharp edge of the limbic brain. Stability means finding people who regulate you well and staying near them.
from A General Theory of Love, by Thomas Lewis, Fari Amini and Richard Lannon. One of my favorite books about the brain.