Dimmesdale's struggle is dark and his penance is horrifying as he tries to unravel his mystery. In Chapter 11, "The Interior of a Heart," Dimmesdale struggles with his knowledge of his sin, his inability to disclose it to Puritan society, and his desire for penance. He knows his actions have fallen short of both God's standards and his own, and he fears this represents his lack of salvation. In an attempt to seek salvation, he fasts until he faints and whips himself on the shoulders until he bleeds. But these punishments are done in private rather than in public and do not provide the cleansing Dimmesdale seeks and needs.
As a sinner, he is weakened to temptation. As demonstrated later, his weakened condition makes it easier for him to associate himself with the Black Man in the forest. His congregation expects him to be above other mortals, and his life and thoughts must exist on a higher spiritual plane than others. Accordingly, his wonderful sermons are applauded by all for a reason his listeners don't understand: Sin and agony have enabled the intellectual scholar-minister to recognize and empathize with other sinners.
In the forest scene, Dimmesdale evidently realizes that he is human and should ask forgiveness and do penance openly. On the way home, he sees how far his defenses have been breached by evil. These thoughts explain why he can so easily write his Election Day sermon, which is filled with the passion of his struggle and his humanity.
