Why do men seem to take advice from other guys seriously, especially warnings about certain people?

Why do some people feel the need to prove themselves physically, especially against bigger opponents? What drives that behavior?
If you have a dream of a friend and they tell you they never want to see you again. What does that mean?
If a man has most of these traits psychologists say are linked to chronic unhappiness in marriage, is it possible for him to change and become a more supportive partner?