We tend to see those we love as greater than they actually are in some ways ignoring their real greatness at times. We deceive ourselves as the result of our own self images. A man who believes he must have a slender, sexy wife might feel betrayed if his wife gains weight. A woman who sees herself married to a strong man may viciously attack him for showing tender emotions or becoming ill. His perceived weakness violates her image of who she is.
People change in the course of their lives.
When we change we act differently than we did during the process of forming our images of how the relationship is supposed to be. A person seeking to improve himself is often sabotaged or ridiculed by friends, family and other loved ones. He has violated the tacit social agreement of how he is supposed to act and who he is supposed to be. In the development of relationships we see people differently than they see themselves. This can be a positive thing if we see the goodness and hidden talents of the other person and help them to develop in these ways.