Paul speaks much about the great truth that all believers died with Christ when He died on the cross (2 Cor.5:14). He speaks about this in Romans, Corinthians and Galatians. "I am crucified with Christ" (Gal.2:20). "If one died, then all died" (2 Cor.5:14). This was a unique revelation that God gave Paul. We don't read Peter, John or James writing about it. When Jesus died and rose again, in God's eyes, all believers died and rose again with Him. Therefore, we can no longer live for ourselves, but for Him alone (2 Cor.5:15).
If you ask believers, "Why did Christ die?", the answer that most of them would give is from 1Cor.15:3, "Christ died for our sins." That is right. But that is only part of the answer. The second part is here: "Christ died so that we should never again live for ourselves, but for Him" (2 Cor.5:15). When we live for ourselves, we frustrate the purpose for which Christ died. If we keep living in sin, we are taking advantage of the fact that Christ died for our sins, and thus taking advantage of the grace of God. Any believer who lives for himself has not really understood the full purpose for which Christ died. Satan's aim is to blind our eyes to the full truth of God. He first tries to prevent us from understanding anything at all about Christ's death. If we do see that Christ died for our sins, then Satan will try to blind our eyes to the full purpose of Christ's death.
Christ died to deliver us permanently from a self-centred life. When we put these two verses together - 1Cor.15:3 and2Cor.5:15 - we see that the root of all sin is self-centredness. A man lives in sin because he lives for himself. As long as you live for yourself, you will never have victory over sin. As long as the root of the tree has not been chopped off, it will keep on producing fruit. If you lay the axe to the root (self-centredness), then you won't have to keep on cutting off the evil fruit (sin) that comes forth.
Many people have got rid of sin on the surface, but the root is still there, the root of living for oneself. You will never get victory over sin as long as you live for yourself. You must decide once and for all, "From this day onwards. I will never make a decision with me as the centre of my life. I will never make a decision based on how it will benefit me." Do you know the number of people who make decisions in Christian work by these questions, "How will this benefit me? How will this benefit my family?" That is how every unconverted, godless sinner in the world also makes decisions. You are then no different fromthem except that he or she is probably an atheist whereas you go to some church. But inside, you are both just the same. Jesus died to deliver us from that, so that we would never make a decision by how it would benefit us, but rather by how it would glorify God and benefit His kingdom and His purpose. If we can get 100 people like that, we can turn India upside down. But it's very difficult to find even a few like that.
The vast majority of Christians haven't understood that we are not to live for ourselves any more. They skip over verses like 2Cor.5:15 and jump to 2Cor.5:17 "Old things are passed away and all things have become new - a new creation." But let me ask you, "What are the old things that have passed away or that should have passed away?" Has "living for self"passed away? Have your ambitions and your goals become new?