If a person fails to be chaste once or twice, or thirty times, they just need to get up and seek chastity one more time, through the Holy Spirit.
Yes, though if one keeps committing the same mortal sins over and over it is a sign. If a man keeps committing adultery 30 times after he’s found the truth of Christ, it doesn’t sound like he’s had a a serious conversion, and runs the risk of inviting more diabolical beings into his life. All sins are personal beings; demons of gluttony, demons of adultery, demons of homosexuality, demons of pride, etc; when we sin they attach to us and we become their slaves. Thus the power of the sacrament of confession as an exorcism.
“If they have escaped the corruption of the world by knowing our Lord and Savior Jesus Christ and are again entangled in it and are overcome, they are worse off at the end than they were at the beginning. It would have been better for them not to have known the way of righteousness, than to have known it and then to turn their backs on the sacred command that was passed on to them…” -2 Peter 2: 20-22
“The man who was healed had no idea who it was, for Jesus had slipped away into the crowd that was there. Later Jesus found him at the temple and said to him, “See, you are well again. Stop sinning or something worse may happen to you.” -John 5:13-14
“Do not be deceived: Neither the sexually immoral nor idolaters nor adulterers nor men who have sex with men nor thieves nor the greedy nor drunkards nor slanderers nor swindlers will inherit the kingdom of God. And that is what some of you were. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.
. . . The body, however, is not meant for sexual immorality but for the Lord, and the Lord for the body. By his power God raised the Lord from the dead, and he will raise us also. Do you not know that your bodies are members of Christ himself? Shall I then take the members of Christ and unite them with a prostitute? Never! Do you not know that he who unites himself with a prostitute is one with her in body? For it is said, “The two will become one flesh.” But whoever is united with the Lord is one with him in spirit. Flee from sexual immorality. All other sins a person commits are outside the body, but whoever sins sexually, sins against their own body. Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God? You are not your own; you were bought at a price. Therefore honor God with your bodies.”-1 Cor 6:9-20
“If we claim to have fellowship with him and yet walk in the darkness, we lie and do not live out the truth. But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus, his Son, purifies us from all sin. If we claim to be without sin, we deceive ourselves and the truth is not in us. If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness. If we claim we have not sinned, we make him out to be a liar and his word is not in us.” 1 John 1:6-10