The natural state of mammals is to be somewhat on guard. However, in order to feel emotionally close to another human being, our defensive system must temporarily shut down. In order to play, mate, and nurture our young, the brain needs to turn off its natural vigilance.
Many traumatized individuals are too hypervigilant to enjoy the ordinary pleasures that life has to offer, while others are too numb to absorb new experiences — or to be alert to signs of real danger.
Many people feel safe as long as they can limit their social contact to superficial conversations, but actual physical contact can trigger intense reactions. However … achieving any sort of deep intimacy — a close embrace, sleeping with a mate, and sex — requires allowing oneself to experience immobilization without fear. It is especially challenging for traumatized people to discern when they are actually safe and to be able to activate their defenses when they are in danger. This requires having experiences that can restore the sense of physical safety.
Van der Kolk (2015)