Do not let sin reign

“Therefore do not let sin reign in your mortal body so that you obey its evil desires.” Romans 6:12
Chapters 6-8 in the book of Romans are one of the most thorough teachings on the effect of sin in our lives, and how to overcome sin by the power of the Holy Spirit. (For those who are interested, a verse-by-verse study through Romans 8 is available from here.) Like it or not, we are all born with a sinful nature, inherited from Adam. Before we were saved, we were subject to that nature; we were slaves to it (Rom. 7:14). Even when we tried to do good works, they were tainted by that sin nature, through selfish motives (Rom. 7:18).
But now, Paul tells us, we have been set free from that sinful nature by the power of God. We have not been set free to please ourselves, but that we might serve God. We have moved from being a slave to one master (sin), to being a slave to another master (God). But whereas the old master only sought to destroy us, our new master loves us and wants the best for us; His yoke is easy and His burden is light (Matt. 11:28-30).
This doesn’t mean that our sin nature is gone. No, it still lingers, seeking to regain control over us through sinful thoughts and temptations, reminding us of our guilt and our unworthiness before God. But here’s the thing that will set you free, if you will take it: we don’t have to give in. We now have the choice whether to sin or not – we didn’t have this choice before. We must never say, ‘I can’t help myself’ when it comes to sin. God has given you the power, through the Holy Spirit, to resist temptation and not be drawn into sin. He has set you free from being its slave, set you free so that you might be devoted to Him.