"I speak my own sins; I cannot judge another." These words were spoken by John Proctor after he had confessed and then recanted that he had the Devil in his life. I think this quote characterizes John for who he really is and not who John is perceived to be in most of the story. At the beginning of the story, we are told that John is somewhat of a feared figure with no tolerance for hypocrites. But, we also learn that he is troubled by his sins and feels like a fraud because his faults or sins are not yet known by others. As the story goes on we learn that John had some sort of relationship with Abigail and that his wife, Elizabeth, knows about it. The conversations between John and Elizabeth show how tense their relationship is and that John feels like Elizabeth has not yet forgiven him and continues to punish him for his sin.
As the story continues and Abigail makes accusations of witchcraft against others in Salem, we learn that the leaders of the court and town think Abigail is a credible person. They believe every charge she speaks of and throw those she accuses, including Elizabeth Proctor, into jail. John is troubled by this as he knows the type of person Abigail is by the sin they committed together. In order to allow the court to see Abigail for who she really is, John confesses to the court the relationship he had with Abigail and tells that Elizabeth saw Abigail as harlot. At this point we see John trying to absolve himself. The court will believe John if Elizabeth corroborates his story. Elizabeth though, does not confirm what John has told the court and we learn that she feels responsible for what happened between John and Abigail. Because of Elizabeth's denial, the court does not believe John's story and ultimately gets John to confess to having the Devil in his life. The court pressures him to confirm others who have the Devil in their life and John refuses.