When I was younger I played sports. As with anything, if you want to do well, it requires training. Sports required physical and mental training. You can train or study for anything as much as you want, but if you are not mentally ready for what you are preparing for, it will begin to show outwardly and the same goes for us spiritually!
This verse is a continuation from Romans 12:1 where Paul strongly encourages us to give everything we have for God. That cannot happen unless our minds and hearts are renewed by God. We can do all the right stuff outwardly, but if the insides are not continually being renewed by the Word of God, we eventually end up being very religious and not truly transformed from the inside out. Pray that the Lord would renew from the inside out so we can genuinely and truly show the true transformation the Gospel of Jesus Christ offers!
Pastor Sean Boehm