Fidelity to me is a crucial element of a relationship between woman and man. I can't imagine to divide fidelity into "physical" and "moral" parts. There is no physical intimacy without spiritual and intellectual intimacy to me. Fidelity is endless trust and devotion, respect and recognition between partners. It can exist only when both partners are equal in a relationship, where there is any kind of dependency (emotional, economical, and so on), there adultery is only a matter of time. The act of adultery means that one of the partners is grown out of a relationship. It is a beginning of the end.
My first marriage failed because of infidelity, I realized that that was something that changed life irrevocably... It poisons everything.