Natural Man is what we once were. Spiritual Man is who we are. What's the difference?
Bad Tree is now good tree.
Old Man is now New Man.
Sinful Nature is replaced with us being partakers of the Divine Nature.
Tare is now wheat.
In Adam is now In Christ.
Dog outside the gates is now "Christ like" son inside the kingdom of God.
Death is now true life.
Child of the father Devil is now Child of the Father God born by the seed of the Word.
Something profound and transformational occurred in us at our New Birth. At the most essential levels, we are now supernatural. This not just because God lives in us, but because something was done to us or more accurately created by God in us.
People are reluctant to discuss this because of the truly dramatic separation that this truth causes between us and the "world". Especially between us and unsaved friends or family. Separation from unbelievers as to our natures is not viewed as a positive by many. At some level, people will assume thinking this way tends to cause us to be self righteous or make us feel so high above others and thus less accessible to those around us who are not born again. People will not want to be around us or feel close to us if we speak this way. Further, to discuss the transformation that has occurred is to separate the real from the mere professor within the church which some would say causes unnecessary division and exclusion within the church.
At the end of his life though, the Apostle John, by the Spirit, made some incredibly significant arguments about the nature of the transformation that has occurred in God's people precisely so that a person reading the arguments could know for certain that they are born again. John was exceedingly keen on drawing sharp distinctions between light and darkness, born of God and born of the Devil, those who know God and those who don't. Through John, the Spirit did this to encourage those who doubt but are truly born again and to convict the rest so that those who are deceived could find true life. He wanted the church to draw those distinctions on an individual and corporate level.
In our sincere goal to allow many, including those who are close to us, to assume they are in the Kingdom and thus give assurance to many, it seems we have lost the true meaning of what it is to be born again. That meaning, however, is very important not only because understanding it helps us have assurance. It is important also because it creates the right expectations in God's people for who they are to be and how they are to think and act as born again children of God. With right expectations or "standards", we are in the right position to pray confidently for all that God wants from us as His children and to have the correct faith to believe that we can in fact be who God has called us to be and to seek, strive, fight and overcome in a way that is worthy of our high calling. John wrote that having confidence in our union and communion in Christ will lead to our prayers being answered in the affirmative. He shared this truth in John 15 and 1 John 3.
Please don't take this to mean that we should have a feeling of superiority to those around us, those who we "once were" as Paul says. If anything, if we approach this rightly, we will be far more humble and far less self confident than the sinful people that we interact with. Further, we will have a far greater hatred for the sin within ourselves than most because we will recognize the stark difference between our own sin and the new nature we have causing us to realize we can be the chief of sinners and the child of God at the same time. We can be the humble, meek and gentle spirit and soul that God created in us.
It seems to me that as we try to dumb down our expectations of the "spiritual man" and reduce Christianity down to the most manageable common denominators possible, that we are doing the people of God a disservice in the interest of mollifying those around us who actually should be exhorted. If we dumb down the way we consider "born again", then our prayer life becomes not so much a prayer of faith for God to give what He has commanded but becomes more about seeking forgiveness for what we feel we are incapable of doing at all. "Grace" at this level then is inadequately defined as merely mercy for sin leaving out the definition of grace that most importantly includes who we are and what God is doing and will do to grow that new life inside us to maturity, into the image of God. The Scripture says we have a new self within us that has been created after the likeness of God in true righteousness and holiness. At some point we have to realize that a branch that is grafted into the vine is indeed a vital and real part of the vine.
Forgiveness is not the only thing that separates the man of God from his unsaved neighbor. Nor is the difference only the indwelling Spirit. The new nature from God that is now ours has given us citizenship and a family heritage in the eternal kingdom of God and that makes it possible for us to see God.
I'm personally reluctant to share all this because it tends to ostracize you from the "loving" contingent of the faith. However, John was the writer who wrote most about the love of God, love of the brethern and love of the world. Yet, he was also the one who wrote most about the new birth and the dramatic changes it wrought.