“God forbid. How shall we, that are dead to sin, live any longer therein?” - Romans 6:2(KJV)
The “sin nature” no longer has the authority to rule over us, i.e. we have died to its authority. However, the “sin nature” is still a resident in our body and we give it power every time we begin trusting in our own strength again which always leads to “sin”.
For instance, when we came to Christ, we came to him spent, i.e. we had tried every way we knew to keep ourselves from doing wrong and we had failed. We had tried every way we knew to find forgiveness and still we felt guilty for things we had done wrong and the thing we were doing wrong. Finally, we heard of God’s love for us and threw ourselves at Jesus’ feet begging for mercy and forgiveness. We received forgiveness, Jesus became our “new husband” and then God gave us his Holy Spirit to live in our heart to change us from the inside out. The typical reaction to this change in the life of a believer is to immediately try to serve God. However, not understanding that the power to serve God is only received by keeping our eyes fixed on Jesus as when we first believed, the new Christian becomes very frustrated by falling back into some of the sins that dominated him before he turned to Christ, i.e. the “sin nature” has deceived the him into believing he can serve God in his own strength. This becomes very depressing because he never seems to be able to rise above his weaknesses. Then the devil throws all kinds of condemnation at him, telling him that he must not be a Christian after all and possibly convinces him to turn away from Christ completely. This is a Satanic delusion, the fact of the believers conversion never changed, but the “sin nature” convinced him that he never was saved in the first place.
The simple solution to this delusion is to return to the humility he began with, fixing his whole heart on Jesus and keeping it there. “For we share in Christ if only we hold our first confidence firm to the end.” - Hebrews 3:15
“We share in” the power of the Holy Spirit to be what God wants us to be. “If only we hold our first confidence firm to the end”.
So, “why do we sin”? We sin when we place our “confidence” in our self.
May God give us all the resolve to hold on to Christ alone that we may walk by the power of the Holy Spirit.
God bless, Orval