The first thing is to know what the goal is as concerning sin. I trust we know it but do not believe, it is possible to achieve, thereby, defeating it already in our mind. Jesus told the woman caught in adultery- go and sin no more. The bible tells us the same thing in various ways starting from Genesis to Revelation. Our Lord God has given us grace through our Lord Jesus Christ. Jesus tells us his strength is made perfect in our weakness. He has even exemplified the way for us to show us that it is possible. The bible tells us as you quoted, walk in the Spirit and you shall not fulfil the lust of the flesh. Sin is not inherent in us and therefore we can get rid of it by holding on to the marvelous grace of God. If we continue to believe that it is impossible, this believe continues to play itself out in us. He cannot tell us to do what he knows it is impossible for us to do.
What you mentioned reminds me of what some people say when faced with challenges of life. We hear some say, “I am not Jesus, or that Jesus is God, am I God?”, forgetting that as Christians, we are supposed to imbibe the mind of Christ. Jesus went through his suffering and temptations without compromising his identity, likewise, we must go through our temptations without compromise as his followers. If we remain true to our faith in the face of the tempiation, the Holy Spirit will walk us through and out of that situation to a triumphant end.
My point is not that we have an excuse to sin, but it is clear we will sin. if we say we have no sin the truth is not in us. If anyone reaches a point of believing they have no sin, the truth is not in them.
It is not about impossible or possible, rather we must practice Righteousness and when (as scripture states we will) we fall short, confess and get back on track quick smart.
God needing to be working in us to Will and to do His good pleasure is a sign we need work! The challenge remains to have the mind of Christ and as we submit to God this is formed in us. Renewing our minds is a process Also.
These are things Christ did not require. He was the way, He is the way. We are not. We are on it and learning as we go, being conformed , sanctified and changing from one degree of glory to another.
Being perfect is possible as soon as we are saved - because He is our perfection. Being righteous as soon as we are saved is possible - because He is our righteousness. Learning to live out His example in this fallen flesh (which is still in the fall) however, Is a life long process and will never end on this earth. For now we know only in part and we must not lean on our own understanding. His thoughts are not our thoughts and His ways are higher than ours.... And so even if our own consciences do not condemn us ...(ie. we think we are sinless)... The word still says we deceive ourselves if we say we have no sin, and the truth is not in us.
Jesus could say He had no sin. He was and still is the truth. This is why I say we are not Christ. To elevate ourselves to a position of professing to be a sinlessly perfect human is Just not biblical.
This is not an excuse to sin. We should strive to resist and turn to God For strength in our hour of weakness full-stop. It is possible not to sin and that is truth. But we stilL do, regardless of what we know or believe is possible.