He always believed in the things his father told him, until he finally realized that Willy was a liar and cheater. After the encounter in the hotel, Biff throws away everything his father had hoped for him, not wanting to please him anymore. Willy put Biff above everything, and tried to make sure that he achieved everything that he himself could not.
Willy's other son, Happy, can be seen as the opposite of Biff, and reflects Willy in some ways. Like Willy, Happy is always seeking attention from his father, and tries to bring up his accomplishments that he thinks will make Willy proud. He also has an older brother that seems to overshadow him in all aspects. Ben, much like Biff had the ability to achieve great things because he was given the encouragement to try. Happy, much like his father and his brother, is seen as the lesser of the two brothers, and is in a constant battle for approval and praise. Even with this, Happy thinks that he is a revered, and respected individual, when very few people really feel this way about him, because just like Willy, Happy could not "reconcile himself with society"" (Loos 19). Happy in this sense becomes Willy, because just like Willy he is seen as the second best, and never gets the attention and love that he desires. .
The big question in this is if Willy's treatment towards his sons either hurt or helped them in the long run. Biff had everything laid out in front of him, but because he saw his father, his idol to an extent, not live out the principles he taught, he lost hope and never fulfilled many of the things Willy wanted him to accomplish. Happy on the other hand never quits, and although he never had the same opportunities as Biff, he did what he thought was best for himself. There were never any expectations for Happy, so he never felt pressure to be more than he could be. This is also seen in Bernard and his relationship with his father, Charley.