Do you know the story of the Tar Baby? I remember reading it a long time ago. The basic gist of the story is that someone wanted to get at Brer Rabbit. So he constructed a baby made of tar. Brer Rabbit comes by and tries to have a conversation with the tar baby, thinking it to be a real person.
When the tar baby didn't respond after the rabbit's repeated attempts to have a conversation with him, the rabbit decides that this person is stuck up and disrespectful by ignoring him. So Brer Rabbit threatens to hit the tar baby if he doesn't at least acknowledge him. Well, his hand gets stuck in the tar. He yells at the tar baby to let go, threatening to hit him with his other hand it he doesn't let go. After hitting him with his other hand, then kicking him with his right, then left foot, then hitting him with his head, Brer Rabbit is completely stuck in the tar. There is no way for him to get out of this fix.
That is one of Paul's points concerning sin in the book of Romans. This is the human predicament. We do not have the strength or the ability to free ourselves from sin. Once you sin, you cannot "unsin." According to God's law, you have broken the law and are guilty. It is like flypaper. Once it has us, we are stuck. The only way to be free is for someone to free us.
The only one who can free us is the very one who died for our sin, Jesus Christ. He defeated sin at the cross, and defeated death at the grave. This is significant because death came as a result of sin (Rom 5:12). Sin's power derives from the law which specifically identifies what sin is (Rom 7:5-8). When we break the law, we sin. At that point, we are stuck. We cannot rewind the clock and "unsin." So the ultimate result is death (Rom 7:9).
Jesus defeated the law of sin and death at the cross and the empty tomb (Rom 8:1-2). He pulled us out of the tar and freed us from the clutches of sin. When does this freedom come about? The power of the freedom comes from the cross and tomb. As to when this freedom comes about in our own lives, it happens when we "die with Him." After describing baptism as dying, being buried with him and raised with him, the text says,
"...knowing this, that our old self was crucified with him, in order that the body of sin might be done away with, so that we should no longer be slaves to sin; for he who has died is freed from sin. Now if we died with Christ, we also believe that we shall live with him, knowing that Christ, having been raised from the dead, is never to die again; death no longer is master over him" (Rom 6:6-9).
When this happens, our sin is done away with, and therefore death no longer has any power over us. We are free from sin and death. Through the death, burial and resurrection, Christ took care of our sin problem and our grave problem.