Before I first got married, I was in a singles class at Church. At one party, we had a before and after contest, where we had to bring some picture that showed us looking completely different. Many brought childhood pictures which were difficult to correlate, but my picture of only a few years earlier won. Even when people went around and juxtaposed the picture with various men, they could not decide who it was. My picture was taken just a few months before I became a Christian.
The picture was of me getting a haircut by my sister. I had very curly hair down past my shoulders. I had grown a long beard, hoping it would be a long Norwegian style beard. Unfortunately, the beard hair was much curlier than that on my head. I needed an afro pick to comb out the tangles. Furthermore, though I was having fun, there was not a hint of a smile. At the time of the party, I had short hair, either no beard, or a neatly trimmed one, and was known for my smiles. Thus, when they compared the picture to me, they were sure it was not me.
When a person becomes a Christian, there should be this startling contrast when the two are juxtaposed. In Romans, it lists many changes. There is the guilty of sin verses being justified (not guilty.) Another is enmity with God a contrasted to peace with God. The book then leads us to dead in our sins, compared to a new life in Christ. From there it takes us to slaves of sin and empowered by the Holy Spirit.
One time I did a study of Peter. I juxtaposed Peter at various points in time after the crucifixion. Each time, he was hiding, and fearful. No matter how much he had seen the risen savior, he was the same. Then came the day of Pentecost. Peter was empowered by the Holy Spirit. He was now fearlessly preaching and no longer hiding in a locked room. This happens to all true Christians. The change is dramatic and keeps growing. The before and after contrast will eventually become unbelievable, if you let the Holy Spirit work.