Death of a Salesman: Theme

"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." p.1630

One thing that I think I am struggling with for this play is the central theme. I was sick today, so I never got to address it with my group. I have a guess, but it is nothing I feel adequately addresses the whole play. I think that the theme can somewhat be conveyed in the quote above. This quote describes the obsession Happy and Willy have to always be number one in life. I think the theme is that trying to be the best always leaves oneself disappointed and short of their goal. Everyone can't honestly expect to be the best at what they do. It is a good goal to strive for, but it is something that only a few ever reach. I think Miller really tries to convey this through the characters Willy and Happy. They never are really satisfied with themselves because they never can feel accomplished in what they do. Biff begins to understand this towards the end of the play and wants to be accepted for who he is. As a result, he seems to be a more composed and level-headed character. Willy and Happy, on the other hand, struggle understanding this throughout the play. This essentially is summarized in what Happy says in the quote above. I don't think I'm too off track with this theme but hopefully my group can help me clarify it tomorrow.