The Bible says that if a person is led of the Spirit they will not fulfill the lusts of the flesh,and show the characteristics of the Spirit,and not the characteristics of the flesh,so they are not under the law,for they are not breaking the law,so the law cannot touch them for prosecution,which this law is the moral laws,laws of love.
So a person cannot say it is not possible to abstain from sin,but if we do sin it can be forgiven us,and if we live in sin for a year it can be forgiven us,for sin can always be forgiven.
But in the flesh dwells no good thing,and the flesh is sinful even when saved,for the Spirit and flesh are contrary to each other.,and Paul said with the flesh he serves sin,not that he is sinning,but the flesh does change,but with the mind I serve Christ,for if we keep our mind on Jesus we can keep the flesh from having it's way.
I would not come across as holier than thou,for like the disciples said when reaching out to people,we are of like passions as you are,and the Bible says what makes you to differ from another person.
Because a person says we can abstain from sin,and have to abstain from sin,by being led of the Holy Spirit,does not mean they might not sin,but realize they should not sin,which is alright in the sense they are not being arrogant,but they should not come across as holier than thou as if they will not sin ever again for they do not know what the future holds,all we can say is I do not want to sin,and help me Jesus not to sin,and mean it,but not come across as arrogant for we do not know what the future holds to be able to say I will never sin again.
Whether a person believes it is not possible to abstain from sin,or they believe it is possible to abstain from sin,we can still take advantage of God's love,and mercy,and forgiveness,knowing He will forgive us,which I have seen people that believe it is possible to abstain from sin,but they would do little sins,but their overall life was basically descent,but a sin is a sin,and I have seen people that do not believe they could abstain from sin,be quite worldly.
So while both may sin the ones that believe they can abstain from sin,put more effort into not sinning,or keep it down quite a bit,while the ones that believe they could not abstain from sin,would put effort in to not sinning,but their belief in not being able to abstain from sin would cause them to slip in worldliness,because sometimes they would not try that hard,on an average.
Whatever a position people take it would be hard to believe that they would abstain from sin for the rest of their life,let's say if they live for 20 more years after being saved,or even a year,for we tend to do little sins that we think it is not so harmful,and does not bother us that much,and can shed it although we might come back to it,which God said love not the world,or the things of the world,even those things that appear to be harmless.
Peter even had a problem for about 14 years,which God did not approve of his behavior for Paul got in his face and told him to stop it,and the Galatians,as well as others back at a time when they were quite zealous to do right,so we do not want to come across as holier than thou,as if we will never sin again for we do not know what the future holds,which God says in the Old Testament of people that think they are holier than thou that they were a stench in His nostrils.
We are not to exalt ourselves even if we can abstain from sin for God gets the glory for it can only be done by His Spirit,although they would be worthy of honor for making the choice to abstain from sin,and mean it,but not to exalt themselves.