Is the feeling of burning after committing a sin considered remorse, and if so, why is it not followed by abstinence and a firm resolve not to return to it? And how does knowledge of the harm of sins necessitate a change in one's state, while many people know their harm yet do not feel remorse?

The feeling of remorse for a sin may not be enough to abandon it, especially if the remorse is not complete. Knowledge of the effects and punishments of sins does not result in abandoning them unless the heart fully realizes this knowledge and senses the reality of the consequences. If knowledge takes hold of the heart and settles within it, it leads to the abandonment of sin. As for mere knowledge of sins, it is not strong enough to resist whims and the embellishment of Satan. The true remorse mentioned by Abu Hamid al-Ghazali is that which overwhelms the heart and prompts repentance.