Nobody is perfect. Everybody is flawed. Ever heard that before? Guess what? It’s not true. The Bible says that there are people that have been made perfect.
Hebrews 12:23 (NKJV) …to the spirits of just men made perfect…
The spirits of every single believer are absolutely perfect. Every single believer is perfect now, because of Jesus. But you say, “I still do things wrong. I still think things that are wrong.“ True, but you’re still perfect. How? Well, it’s your spirit that is perfect, just like Jesus now. If you don’t see things perfect in your life, it’s not that you’re NOT perfect, God just wants your perfection to manifest through you.
Romans 12:2 (MKJV) And do not be conformed to this world, but be transformed by the renewing of your mind, in order to PROVE by you what is that good and pleasing and perfect will of God.
When it says that you may “prove“ the good, pleasing, and perfect will of God, that’s saying that you will give “evidence” of the good, pleasing and perfect as you renew your mind.
Romans 12 is acknowledging that you HAVE what is good, pleasing, and perfect, but you just need to renew your mind to what you have, so that it can be manifest (or so that it can be “proven” outwardly). But regardless of what you see right now, “good, pleasing and perfect” are now words that describe you in Christ! What a wonderful gift from God!
And put it this way, if Jesus went to the cross to do a work for you — if He came to make you a new creation — and you’re still not perfect… Jesus must’ve missed something. You are the result of Jesus’ finished work. If you’re not perfect, Jesus did not do a perfect work.