How does Stevenson emphasize the difference between Jekyll and Hyde at this moment?

In Chapter Ten, we learn that Jekyll's dual life was going perfectly as planned until two months before the murder of Sir Danvers Carew. One night, he transformed into Hyde involuntarily, while sleeping. When he realized that he was in great danger of being trapped in the body of Hyde permanently, he determined to live only as himself and was successful for two months. When the time came that he felt the need to free his evil side, he took the potion in a moment of weakness. Hyde emerged, and after months of repression, was out for blood. On this fateful night, Hyde murdered Sir Danvers Carew, beating him to death with one of Jekyll's canes. Hyde felt no guilt, but even before he had completely transformed back into himself, Jekyll was asking God for forgiveness.