He remained honourable and immovable, by remaining true to himself and what he believed in. The on-going quality Proctor's character holds is the normal and healthy imperfections a person should experience. He makes genuine and human mistakes, which makes him more approachable as a person because he appears natural in his ways and respectable within his decisions. Except for the last one he made. He wouldn't sign a lie because he was too passionately committed to his beliefs, and in some ways this was his major weakness. As it led to his death. He didn't want to lose faith in himself by lying and he didn't want the puritan people to look at him and see him as a coward. He believed that a person could learn from their mistakes and redeem themselves by doing good. After the crime he committed he was just the same, a person because he was a symbol of goodness from the very beginning of the play.
The situation gets a bit sacrificial when Abigail thrives for her revenge and begins to get besotted with John. She believed that even if goody proctor wasn't around John would still have feelings for her, as he did during their previous affair. It was obvious that Proctor was attracted to Abigail and that she was in love with him, however wrong it may have been morally. Perhaps he didn't make it clear that it was over, he was also quite weak in that respect. Maybe it was her narrow mind preventing her from seeing how circumstances and how people in them can change for what they believe is right.
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"Give me a word John. A soft word-.
"John I am waiting for you every night.".
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Abigail uses taunting and forceful tactics to make him see "Sense", interfering with his beliefs; all of Abigail's dialogue is based on her fiction and what she believed in.
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He slows down the process of doing what he thinks is the right thing, which then led him to oppose and challenge elements beyond his control.