If either one is thinking of divorce. If either is drunk. If either one is thinking of another person of the opposite gender, etc. These are all situations that speak to hearts and minds that are not totally committed to and engaged with each other. Nachmanides, a 12th century commentator, in a letter written to his son in preparation for his wedding, underscores the emotional component of intimacy without which, he states, the conjugal human experience is lowered to one more consistent with animal behavior.
Thoughts are the crucible of our expressed emotions as well as our behavior.
Not necessarily where one is physically standing, but rather where his thoughts take him. The congregant, in great bewilderment, protested that he hadn't traveled anywhere. While it is true that the email relationship in which the writer's husband is engaged is not a physical one, it obviously occupies the focus of his thoughts and thereby constitutes a breach of intimacy between husband and wife. Shared feelings and communication are the currency of intimacy. The better part of him is absent, and the exclusive intimate relationship has been compromised.