A recent revelation of developmental neuroscience is the understanding that the brain was designed, by evolution, to be an organ shaped and programmed by the environment it is situated in. The brain is in essence a social organ, with a central role played by human interactions. While the development of language allows us to connect with each other via language, via the conscious operations of the left hemisphere, we first communicate to others in a non-symbolic manner, through body language, facial expressions, glances, tones of voices, under the control of the right hemisphere. In successful encounters our emotions are signals that sync us up, establishing security, emotion regulation and social communication. When we are attuned to another, or "emotionally locked in" with or "mirrored" by others, we can temper states of excitation and move slowly into vulnerable situations that might previously trigger dissociative episodes.
Skillful caretakers provide this mirroring, along with ideals to aspire to, a sense of safety, a sense of membership in a community, a resource that reminds us that our feelings are understandable and not invalid.
Interactions with caretakers, when we are young and vulnerable, install that processes that allow us to regulate the shifting states of arousal that arise and pass within the body and mind. Emotions are communications of our inner states to others, and without being read and mirrored (signaled back to us) we will find certain emotions difficult to experience later in life. The emotional tolerance of caretakers create an ability to feel and communicate stress levels, which in turn allows us to form skillful responses to cope with inner stress and outer triggers. (Note that any new, unknown situation can be experienced as stressful and thus need regulation). Our capacity to approach, tolerate, and incorporate new, unfamiliar challenges in life, to explore the world, is founded on support; without people we are attuned to, we will be too anxious to investigate all the opportunities that surround us.
On the other hand, when those we reach out to for human connection pull away, shame or reject us, these encounters can etch trauma maps—the expectation of abandonment—into the right hemisphere; in short we come to expect and seek out others who will dismiss us. The emotion regulation region (the orbito-frontal region of RH) fails to synaptically connect with excitory circuits, leaving us vulnerable to fight, flight or freeze impulses. The interpersonal result can be what's referred to as repetition compulsion, seeking love and acceptance from those who cannot provide it; trying to purchase orange juice from the hardware store.
We can apply these ideas to human care taking and therapy; the idea is to create a safe container or holding environment that facilitates the full expression of the entire emotion palate, from the pleasant (joy, happiness, confidence) to the challenging (fear, loneliness, protest, agitation, etc). The full range of emotional energies must be tolerated for optimal development to occur; environments that only tolerate a limited segment of human traits are growth-inhibiting and effects the development of the right hemisphere's ability to regulate (feel, share and control) emotions. The brain is experience driven in its maturation process.
And so we arrive at a modern conclusion that the environment impacts on biology, as well as vice versa; social integration creates a feedback loop, where it writes itself onto the brain and determines how we interact with others. So spiritual and emotional progress depends on both internal and external work: creating a safe space for difficult emotional energies; connecting skillful with those who can connect with and tolerate our human experience.