In addition to intimacy skills, it helps to understand the science of our brain; specifically, the way our brains react when we feel threatened. Unconscious fight/flight/freeze responses can hijack even the best intentions.
It comes back to the ‘hardwired to belong’ part of our biology. In relationships, our biggest threat, what we’re most afraid of, is being rejected or abandoned. To avoid being left or told to leave, we may leave the relationship ourselves. This means that even though we have a drive for closeness and connection there is an imperative drive within us to protect ourselves from threats. As a result, if we’re not aware of our brain’s function to protect us, we may act in ways that work against our best interest, against our relationship.