How does a servant know that he has resolved not to return to sin, and is there a way to achieve this condition, and what are its signs?

The resolve not to return to sin is a firm intention and a definite decision on the part of the servant not to repeat it. This resolve, along with immediately abandoning the sin and regretting it, validates repentance. This resolve is achieved by contemplating the ugliness of the sin, its evil consequences, and how it leads to Allah's displeasure, which then engenders sincere regret. This regret is true repentance, and it necessitates the resolve not to return to sin. Among the signs of the validity of this resolve is taking the means that aid in repentance, such as avoiding the place of sin, forsaking bad companions, choosing righteous companions, and striving to rectify deeds and increase in acts of obedience.