In Arthur Miller's play Death of a Salesman the character of Willy Loman represents the sad reality of those who establish goals with the wrong aim, and those who live life in self-denial.
Willy is a man who, from the very beginning, has blatantly denied his own talents, abilities, likes, and hopes. He gives everything up in favor of following the dreams of a man he has heard of, who is supposedly quite successful and well-liked.
This being said, Willy dedicates his entire adult life to the pursue of a dream that is not even his own. As a result, he fails to build a foundation of purpose, and meaning in life. Instead, he goes from shallowness to superficiality, entering empty relationships, following false dreams, and providing nothing of importance for his wife and children.
It is no wonder that, now approaching his golden years, Willy Loman has achieved nothing. The biggest evidence we have of this is when Willy is found in the middle of the night trying to plant new seeds in his garden. While he does this he is quoted as saying
I've got to get some seeds. I've got to get some seeds, right away. Nothing's planted. I don't have a thing in the ground."
Arguably, Willy has nothing left but....his dreams! It is no wonder than this is the only retreat that he has to build upon the very little that he has laid out. One must remember that Willy's dream area mixture of memories and "what if's". When a man has nothing left to do but dream, then he must dream or die.
The opportunity to re-create reality through his hallucinations gives Willy his last chance to make peace with his past, his present, and his future. It is the only break he gets to forgive his life, and himself. The channeling of his emotions can only happen in private, and facing all the ghosts that consistently haunt him.
Therefore, the retreat into what could have been, or what was once conducive to greatness, is Willy's last oasis before his death.