Reddit reviews Affect Regulation and the Origin of the Self: The Neurobiology of Emotional Development

It is too much to go into here. You can read more about it in Berceli's book, along with Liz Koch's psoas book, also her core awareness book Staugaard Jone's "Vital Psoas" book, and Alan Schore's work is good.

Attachment and object relations are important concepts in the conception of personality disorder, but they are a bit outdated in the sense that these concepts have been somewhat refined.

You can find more modern conceptions in relational psychoanalysis / mentalization theory (e.g. Fonagy/Target -- Attachment theory and psychoanalysis, Attachment and reflective function: their role in self-organization).

Or interpersonal neurobiology. For example, this article by Daniel Stern, this one by Daniel Siegel, and something by Allan Schore, like this or this).

Here's another decent overview article