Willy Loman is a character who is above all profoundly unaware of the kind of limitations and weaknesses that he suffers as an individual, and this is what distinguishes him from other tragic heroes, as he fights so desperately to preserve his various illusions of success, and eventually goes to the grave in order to maintain his elaborate fictions. He is the only character in the play, perhaps apart from Happy, who does not realise at the end of it that his last name is a symbolic representation of the kind of position Willy occupies in society: a "low man."
In addition to being blind to his own true nature in the play, Willy is also blind to the way in which his own family try to reach out and love him, regardless of his failure or success. The play in part presents Willy's inability to accept this love as the crowning tragedy of his day, much more significant than being fired. However, let us remember that Willy does chose to end his life for love of his family, as he kills himself so that he is able to leave a legacy which, he believes will give Biff the ability to succeed where Willy himself failed and achieve the American Dream of elusive success, fame and wealth.
It is worth paying particular attention to the death of Willy. After slaving away for so many years trying to sell goods, he finally comes to understand that the most valuable product he can "sell" is himself, thanks to the help of the advice of Ben. In this regard, the earlier comments of Charley strike us with particular significance:
...after all the highways, and the trains, and the appointments, and the years, you end up worth more dead than alive.
Willy does then move towards a kind of epiphany as he realises the truth of this statement at the end of the play. And this is, above all, the ultimate irony of the play: Miller presents us with a system that is so dominated by capitalism that a man is worth more dead than alive, and the gift of life is balanced against a material sum of money and found wanting.