I have a friend who is high up in the army where he has been serving his people for about ten years now. He was married about a year ago. He sees his wife on the average about once every two weeks. I asked him how this affects his shalom bayis [I assured him that I studied marriage counseling and that it is really none of my business:-)]. He told me that if they wouldn't both believe in the incredible service he is doing for am yisrael their marriage would be in the dumps but since they both realize the value of his job, it is manageable.
THAT is mesirus nefesh!