Such an admission would ruin his good name, and Proctor is, above all, a proud man who places great emphasis on his reputation. John Proctor is one of the key characters in "The Crucible" and can be considered the leading male role of the play.
Hale says this argument is so important Danforth should let a lawyer If he didn't have them, he wouldn't be a tragic hero. In addition to struggling with the weight of his sin, the fact that he must reveal his transgression torments Proctor.
Proctor assures him his evidence is valid, but Ezekiel Cheever mentions that Proctor earlier ripped up Only through his public acknowledgment of the affair does Proctor regain his wife's trust. He is ashamed of this, and clearly shows that he does not want to repeat such an incident in the future.
Proctor was super ill, btw and, before he knew it, his good life was bad, bad, bad. He dreads revealing his sin because guilt and regret already overwhelm him.