No, Christians don't claim to be without sin, actually 1 John 1:9, says, "if we claim to be without sin, we lie and the truth is not in us" most of the time this question comes up because a Christian has a habitual sin, they are dealt a guilt card from the enemy as being helpless and a failure in front of God, of course the enemy is an accuser of the saints and we have an advocate with the Father, Jesus Christ to stand for us.
The revolving sin drives a person to try all sorts of things to stop it, they are willing to quit but keep on getting driven into it. Looking for an example in the Bible of how to handle something like this is found in Romans 7:19,24 whereby Apostle Paul states something similar "for what I do is not the good I want to do; no, the evil I do not want to do, this I keep on doing, what a wretched man I am". Obviously Paul needed JESUS to solve the problem as we all do, and Jesus said My grace is sufficient, you can't handle it by human efforts is the bottom line.
We need to know what is the driving force behind the compelling urge to sin; of course we need wisdom to direct us. When faced with this issue, you will need older Christians who have encountered this facet in the past that can help you in strong prayer, and other insights that the Lord has given them in previous counseling. Deliverance from a stronghold in your mind can be one answer for sure.
1 John 1:9 is a scripture for Christians to hold onto during times of storms when you are under attack. As an anchor to be defined, Romans 10:13 says, "everyone who calls on the Lord will be saved. Don't let others who don't have the victory on this subject be a downfall to you. Here are some scriptures to hide in your heart:
See: 1 Peter 5:10, Colossians 2:14, Revelations 21:4, Ephesians 2:8, Romans 12:2, Titus 3:5, John 3:16, 2 Corinthians 4:17, John 15:1-27, 1 John 3:9.