In NOT "Just Friends," infidelity is any secret sexual, romantic, or emotional involvement that violates commitment to an exclusive relationship. An emotional affair, in fact, can be even more destructive to a marriage than extramarital sex. An extramarital affair that involves both sexual intercourse and a deep emotional attachment poses the greatest threat -- and this is the kind of intense infidelity that is becoming more common. In the new crisis of infidelity, more men are getting emotionally involved, and more women are getting sexually involved.