Proctor's development can be construed as a journey toward a specific kind of self-discovery.
At the opening of the play, Proctor is a fallen man, having had an extra-marital affair with the family servant, Abigail Williams. Proctor's wife has trouble forgiving him and Proctor struggles to rehabilitate his pride and sense of self-worth.
In the end of the play, Proctor discovers that there is still a chance for him to act with integrity and to leave his children with an honorable legacy. He is given this revelation in the form of a choice, as it turns out, when he is posed with the dilemma of whether or not to sign a false confession. Signing the confession will save his life, but will be dishonorable, stripping him of any hope for pride.
This struggle is descriptive of Proctor's conflicts throughout the play as he strives to earn his wife's forgiveness, to relinquish a false pride for a real one, and find a way back into a sense of self-worth.
When Proctor has his final conversation with Elizabeth, these are the issues he discusses. Proctor sees no use in standing on principle when he is such a low creature, but Elizabeth helps to convince him that this is not so. She says at one point:
“Whatever you will do, it is a good man does it...”
This is the end of Proctor's journey of self-discovery, realizing with his wife's help that he does have value, specifically, he has moral value. His journey toward self-acceptance is complete when he goes to the gallows with his integrity and pride intact for the first time in the play.