The one new man (Jew and Gentile one in Messiah) is a very important goal that we as the people of God need to keep ever before us. Yeshua prayed that His people would be one for a very specific purpose (John 17). So that the world would know and believe that the Father sent His Son and has loved them.
Our oneness with each other in Him speaks volumes to the world. If we claim to want to see people saved from their sins and receive eternal life, to know God and Jesus Christ/Yeshua the Messiah, then we should want to be one with every fiber of our being.
But the truth is that this goes completely against our nature. Yes, it is an act of the Spirit, not the flesh. We must allow Him to work it in us. We must allow Him to mold us as the clay we are. That is the only way it is possible.
We must live in the power of the Spirit and be submitted to His Torah/Law (Romans 8) so that we may please Him and become one, completely one. This is not just a half way thing, it is an all the way thing. We either are or we are not.
Let us put off the old man and put on the new and be submitted to His will, not ours. If we know what pleases Him and still look for excuses not to be what He wants us to be then what is that?