Yichud: The Foundation of Awe and Self-Reckoning: 3a

It is the way of Hashem to pour out good on his children who have erred and sinned. By doing so it leads to the sinner having deep regret. When seeing that Hashem in His glory still wishes to have a relationship with him his heart is broken due to his mistake and he contemplates how not to return to his mistaken ways. There is no comparison between this type of regret, which comes from a loving relationship with Hashem, and one that comes from someone who is down because of his sin.

There is a parable about this from the Baal Shem Tov. There was once a villager who spit upon the statue of the king. The king took him and appointed to him to a governmental post. Over time he promoted him to higher and higher positions. The nicer the king was to him, the more he raised him up, the more he learned about how wonderful the king was, the worse he felt that as a lowly villager he had demeaned the king like that. He deserved a punishment and the king was being nice to him. The king realized that if he had killed him the villager's suffering would have lasted a moment. Now he was filled with constant suffering as to how he could possibly have done such a thing. This is how Hashem deals with our wrongdoing as well.

This only works for a contemplative person who stops to think about what he has done and realizes now the greatness of the king. Has he been a fool and seen that after his behavior the king was kind to him, he would have concluded that offending the king or being respectful was all the same - the king doesn't care.