why is happy satisfied with his life?

In the opening scenes, Happy appears more content than Biff, but at the play's end we see that he's been drawn into his father's illusion, pledging to take up his father's cause and succeed where his father had failed. While after Willy's death Biff recognizes his father's failings, Happy wildly proclaims: "I'm gonna show you and everybody else that Willy Loman did not die in vain. He had a good dream. It's the only dream you can have to come out number-one man. He fought it out here, and this is where I'm gonna win it for him."