While people often have intimate friendships with other people, especially of the same gender the emotional affair is very unlike. It really does have a blow in the marriage because of the intimate tension involved and also due to the fact that the person having emotional affairs is sharing intimacy with someone else that best belongs within the marriage.
The idea that marriage is a union and that your spouse is the person you would share with the most gets corrupted when a spouse starts sharing this with someone else. The amount of time a spouse thinks about this person outside of the marriage instead of his/her partner is fully out of proportion with how things should be. If a spouse is not the person you are thinking about most and in intimate way, it signifies a marriage with serious problems.
