The most important thing that John Proctor learns about himself by the end of this act ?

Act 2 

Proctor finally learns that he must face his sins. Cheever takes Elizabeth away. Proctor demands that Mary Warren come to court with him and charge murder against Abigail. She warns Proctor that Abigail will charge him with lechery, but Proctor insists that his wife shall not die for him. He knows that he will confess his lechery to save his wife. Mary Warren sobs that she cannot go against Abigail.