Even though I am a "new creation" (II Cor. 5:17), set free from the tyranny of sin (Romans 6:6-7), I still sin. All Christians do. Romans 12:21 says, "Do not be overcome by evil, but overcome evil with good." The Apostle Paul would not have to write that if we stopped sinning when we believed in Jesus. In fact, you could throw out most of your Bible if sin was no longer an issue for Christians. It is indeed, but the good news is, we are not alone in our fight to overcome evil with good. In fact, we could not fight if it was left up to us, but the Holy Spirit comes and helps us in our weakness. Living according to the Spirit , setting our minds on the things of the Spirit, gives us life and peace (Rom. 8:5-6).
How could Jesus say in Matthew 11:28-30 that his yoke was easy and his burden was light? How could He say that we could find rest for our souls? Is your soul rested today? He knew that He was leaving with us "the Helper, the Holy Spirit, [who would] teach [us] all things and bring to [our] remembrance all that I have said to you." (John 14:26) And in His next breath, He gives us peace (vs. 27), He leaves us with His peace.
I think we (or I, at least) look more like the "before" than the "after" because I try so hard to be good, all by myself, and forget to set my mind on the Spirit who dwells in me. I forget that Jesus has promised peace, and there is no reason for my heart to be troubled or afraid (vs. 28). I am too much like Peter, looking at the winds and waves around me instead of focusing my gaze squarely on my Savior.
One day, we who believe in Jesus will all be glorious "afters", when we leave this earth and go to be with Him. In the mean time, we are slowly being made more like the "after" we long to see. I'll leave you with these thoughts:
Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom. And we all, with unveiled face, beholding the glory of the Lord, are being transformed into the same image from one degree of glory to another. For this comes from the Lord who is the Spirit. - II Corinthians 3:17-18
So we do not lose heart. Though our outer nature is wasting away, our inner nature is being renewed day by day. - II Corinthians 4:16