I speak from experience. And perhaps you missed the bit where I said: Even though we are saved/born again and washed clean we all need our feet washed from time to time.
Christians already know that they should not sin so preaching against it is perhaps a waste of breath but new Christians especially need to know how to deal with it when they do something wrong or have a bad attitude as they surely will. It's ok to preach against sin but you also need teaching on how to deal with sin in you walk with God. And this seems to be something that is often lacking in discipleship.
I believe that the main teaching on how to deal with temptation is a type of reverse psychology that the Lord uses on us when we come to the knowledge of His grace in our lives.
The law has the effect of exacerbating temptation as a kind of "forbidden fruit" or "wet paint" principle.
When we are told not to do something, the flesh rises up within us and says, "I can do that if I want to".
But grace takes away the penalty of sin and so the law is no longer an element that presents to us "forbidden fruit"...because now there is no condemnation for them who are in Christ Jesus (John 5:24 (kjv))...and those who are in Christ do not walk after the flesh but after the Spirit (Romans 8:1 (kjv)).
So then, because there is no condemnation for us, the law now only behaves as a set of wisdom principles rather than a hard taskmaster that condemns us when we fail.
Therefore, the principle of the law, that it produces all manner of concupiscence (Romans 7:7-13) has been dealt with by the concept of grace.
The more we realize that we are not condemned if we violate the principle of the law, the more we find that temptation no longer has any sway in our lives.
But until we come to that understanding, it is also important that we resist temptation (see James 1:12-16, 1 Peter 1:6-7) and learn that the only way we can overcome sin in our lives is through the grace of God; which also enables us to resist temptation when we lose sight of the fact that we are covered by the grace of God. Because the devil then comes in and tells us that we are covered by the grace of God even if we sin...after that he has btought in the law to exacerbate sin...thus he turns grace into license.
So we must at the point that the law has come in, seek to resist the devil and he will flee from us. We must seek to come back to the understanding that we are covered by the grace of the Lord without falling back into the temptation of thinking that such grace is a license to sin...
It is a fine line that I still find sometimes that I do not know the way to escape. I find that it is necessary to never allow the law to come in and tempt me rather than attempt to deal with that temptation after the law has had its effect of making that sin appealing.
And the Lord has given me the victory over a short period of time. I find that it is wisdom to be on guard against temptation any time that I begin to think that I am standing and doing well (1 Corinthians 10:12-13).
A good word in all of this is to remember that if we take advantage of the grace of the Lord and sin; when we know that He has given us grace so that if we do sin, it will not be to our condemnation; that we are in effect insulting the Spirit of grace and taking grace for granted in our lives.
Therefore to sin willfully would be out of the question; while if we sin unintentionally or ignorantly, we find that the grace of the Lord is there and He will pick us up when we fall. For the righteous falls seven times and gets back up again; but the wicked fall into mischief--Proverbs 24:16.
Also, see Psalms 37:23-24; but consider also that in the New Testament we have it even better, in Jude 1:24, 2 Peter 1:10, and 1 john 2:10.
