Litlove's comment below about the British psychoanalyst Donald Winnicott and his concept of 'transitional space'.
I remembered reading Winnicott back in the 1970s, when I first became interested in psychology and psychotherapy - someone rather humane and progressive, less grating on a feminist than most of the mid 20th century 'mother and child' merchants. Details had faded, though, so Friday lunchtime found me in the workplace library. They don't study humanities where I work, so although I'm right next door to a big library, I rarely make much personal use of it. They do study psychology, though - social psychology, but social and clinical clearly overlap. So there was plenty by Winnicott, it transpired. I went home with a couple of not-too-heavy collections of talks and articles and spent some of the weekend reading them. Reading and wincing, because here is a story told in elementary terms of 'good enough' parenting and consequent normal development, and I know a lot of it was not my own experience. It's dispiriting, but horribly fascinating to contemplate how long ago it all went wrong.