Willy Loman is concerned with himself more than anything or anyone else. He is apparently a good provider until we meet him later in his life, and that seems to justify his bad behavior and unfaithfulness. Willy does not respect women, and he has taught his sons to be like him. He is a stereotypical salesman who will do whatever it takes to close the deal in every area of his life. When he gets caught he is unable to apologize or make amends, for that is something men do not do according to his world view. He is also unable to talk about what is happening to him (forgetfulness, diminishing sales, thoughts of suicide) because he thinks it will make him look weak. He is of the opinion that silence is strength, but he loses his family and eventually his life because of that silence.
Willy Loman seems to believe that financial success is the true measure of moral success. To be a good person, one has to make money.
This value system may simply be a response to Loman's moral failures as a husband and father which serves to deflect his real guilt and transgressions onto a playing field over which he has little control.