What are the sins for which repentance is obligatory, and how can one remain steadfast in repentance and not return to sin?

The servant must repent a general repentance from all sins, those known and those unknown, because what is unknown is greater. His ignorance does not excuse him if he was able to acquire knowledge. This is considered part of the generalization of repentance, which includes everything the servant has not brought to mind from his sins. General repentance includes a general resolve to perform what is commanded and abandon what is forbidden, and a general regret for every forbidden act. Among the greatest aids to repentance are resorting to Allah and seeking His help, and searching for righteous companionship and an environment that assists in this, by abandoning places and people who were a cause of sins.