This is a phrase I have been using when I teach about couples therapy. It reflects two prominent models in couples work: differentiation-based and Emotion-Focused (attachment-based). Differentiation is the ability to be close to others without losing yourself (of course, this means not losing your Real Self). Attachment is the belief that our partner will be there for us, especially if we feel emotional vulnerable.
When we combine these two emotional/psychological states, we have an amazingly intimate relationship.