John Proctor's sacrifice of his life was necessary in order for him to move beyond the guilt he had imposed on himself. Proctor is a tragic hero - meaning, one trait or quality (in this case his reluctance to reveal his affair with Abigail, and, further, to truly admit his responsibility in the matter) causes the downfall of the character. John Proctor's failure to share with Rev. Hale and the rest of the town the truth he knew about Abigail early in the play is what led to his wife Elizabeth's accusation from the girls. When, as John is walking to the rope, Hale shouts to Elizabeth to talk sense it to him, Elizabeth states, "He has his goodness now. God forbid I take it from him." Elizabeth recognizes that this sacrifice was necessary for John to fully forgive himself for his sins. And, it's also important to note that the audience's reaction most likely sticks with them for a while following the end of the play. John's sacrifice is necessary to fully illustrate the hypocrisy of the witchtrials and to relieve him of his guilt.