Willy's relationships are all failed. This is true largely because Willy seems incapable of dealing with reality. He does not engage with Biff as a person, but with Biff as an idea, as a bundle of potentialities. Though his relationship with Linda is better, it is still not good. He has cheated on her. He has been dishonest and continues to be dishonest. The lies he tells her are just another part of his pattern of behavior wherein we see Willy choosing to engage with fantasy instead of reality.
Perhaps Willy is best defined by his name itself. When we look at his mental characteristics, his physical characteristics, his employment record, and his relationships to others, he is certainly a "low man." His view of life and the world around him is certainly idealistic--some might say hopelessly idealistic--as it creates more problems for him than benefits.
Willy's job as a salesman identifies his own life. He tries to sell everyone, especially his family, on his own ideas and beliefs. When he sees his job slipping away, he also realizes he has lost control of his family as well.
Willy is totally idealistic, and he has a vision of what success means to him. Unfortunately, his vision does not match the life that he lives, and he cannot deal with the disconnect between his illusory dreams and the reality of his circumstances. His compromised view of himself is then posited onto other characters such as his two sons which complicates the relationship that Willy has with them.
i think willy is considered to be a new version of the tradition tragic hero's whose flaw lead at the end to his downfall.willy ,maybe,is a good natured man who loves his own family so much and who is ready to sacrifice his life to make his family,especilly Biff,happy and comfortable .But has a great flaw.all his measures about success are totally corrupted.he think that to be popular and to well liked are all what you need to become successful,neglecting the main essence of success that is happiness,his dream of success is totally material and artificial.