One possible view of this play is to judge Willy very harshly. He clearly lives his life in the wrong career and suffers himself as a result, in addition making his wife and children suffer from having "the wrong dreams," as Biff says in the Requiem. He lives his entire life chasing the American Dream, no matter what that drives him towards, and finally he is left with the implacable logic that for his life to be "worth" something he must kill himself in order to gain the insurance money and have something tangible to show for his life.
However, if we look at Charley's view of Willy in the Requiem, there is another way of thinking about Willy's character. Note what Charley says:
Nobody dast blame this man. You don't understand: Willy was a salesman. And for a salesman, there is no rock bottom to the life. He don't put a bolt to a nut, he don't tell you the law or give you medicine. He's a man way out there in the blue, riding on a smile and a shoeshine. And when they start not smiling back--that's an earthquake... A salesman is got to dream, boy.
Charley manages to imbue the profession of being a salesman with a curious romanticism, suggesting that there is something mythic about the profession, as salesmen are "out there in the blue," and yet at the same time it identifies the limited, tragic nature of the salesman as well, as he only has a "smile" and "shoeshine" to protect him and to sustain him. Whilst such a view does recognise the tragedy of Willy's life, it also shows the way that Willy had to dream and had to hold on to those dreams, as psychologically, it is suggested, Willy had nothing else to cling on to. Willy's motivations in this sense are not nonsense, but a survival strategy that prevent him from facing the emptiness of his own life.