And be renewed in the spirit of your mind; And that ye put on the new man, which after God is created in righteousness and true holiness.
Ephesians 4:23-24 (KJV)
The moment we give our lives to Jesus, we receive a new nature. Our spirit is made perfect through being unified with the Lord. The day to day task of every Christian now becomes to be renewed in the spirit of our mind. This means that we must deliberately and intentionally put on our new nature which after God is created in righteousness and true holiness. Simply put, we mediate on who we are in Christ. We no longer look to who we are in the flesh, we look to who Jesus has made us to be. The more that this becomes our meditation, the more we will begin to live according to our new nature. And when this happens, we will bear much fruit in His name.