When he leaves his comfortable home to set out on his adventures as a knight-errant, Don Quixote dreams of a romantic life of chivalry, one filled with acts of courage as he rights the wrongs in the world. By the conclusion of the novel, however, his life can be interpreted as one that encompassed elements of tragedy.
The idea that Don Quixote sacrificed "what might have been" in his pursuit of a world that did not exist, except in his own mind, is introduced near the end of the narrative. When he comes home after being defeated in a mock battle intended to bring him home to safety, Don Quixote is surrounded by those who love him and worry about his well being. His loyal housekeeper of many years begs him to take care of himself:
. . . stay at home, attend to your affairs, go often to confession, be charitable to the poor, and let it be upon my soul if any harm comes to you as a result of it.
When Quixote complains of feeling ill, his housekeeper and his niece respond with concern:
And good daughters that they unquestionably were, the housekeeper and the niece helped him up to bed, where they gave him something to eat and made him as comfortable as they could.
When it becomes clear that Don Quixote is dying, the two women are filled with grief:
At this news [they] . . . were so overcome with emotion that the tears burst forth from their eyes and their bosoms heaved with sobs; for . . . he was always of a kindly and pleasant disposition and for this reason was beloved not only by the members of his household but by all who knew him.
Losing himself in the world of "those hateful books of chivalry" had cost Don Quixote his life as it might have been lived in his final years, surrounded by all who loved him best and deserved his attention.
As he faces his death, Don Quixote realizes what he has sacrificed:
I see through all the nonsense and fraud contained in [books of chivalry], and my only regret is that my disillusionment has come so late, leaving me no time to make any sort of amends by reading those that are the light of the soul.
His final days are spent drawing close to God who had given him "so many blessings" and in making amends to those he had abandoned. One of the tragic elements in Don Quixote's life is that he wasted so much of it pursuing false dreams. All the good he could have accomplished at home and the happiness he could have enjoyed were never to be.