My dad said that in his career he saw a pattern. The spouse leaves, and the spouse left behind creates a whole new life. Part of it is a defense against loneliness. Part of it is a way to make time go by faster. But, new jobs, new hobbies, new schedules open the door to new friends, new intimate circles, and more often than people will admit, new lovers or friends of the opposite sex. This creates a whole new life of which the absent spouse is not a part, and when he or she returns, isn’t necessarily welcome.