What are the situations that invalidate or corrupt repentance?

Sincere repentance fulfills its conditions: giving up the sin for the sake of Allah, regretting it, and resolving not to return to it. If these conditions are met, the repentance is accepted. If the servant returns to the sin after his first repentance, his previous repentance is not invalidated. Rather, he must offer a new sincere repentance. And whenever a servant sins and repents, Allah forgives him, even if the sin and repentance are repeated many times, for Allah forgives the sins of those who repent from them.