A car driven by a drunk driver can kill and cripple people. The same car, driven by a paramedic, saves lives. Two powers fight to control our minds and bodies. We choose our master by whom we obey.
Every time we obey sin, it gains a stronger grip on us making it harder to resist next time. Every time we obey God, righteousness becomes stronger in us, making it easier to obey God. Obeying sin leads to enslavement and shame (Rom. 6:19-23).