If it is as you say then what is overcoming sin all about? What is the law of the flesh?
First, it's not what i say, but what paul has said. Second, Jesus overcame sin "for us" on Calvary, right. We overcome sin when we are "in Him", and He is "in us". We are "in Him" when we faithe into Him. We Faithe into Him by a continual surrendering of our lives to Him, and living a life inspired by that surrender. This is the state of Sanctification, (separated from our sinful nature), and Justification,( to be just like Jesus ). This is the state of being paul is describing in Rom. 7:14-21 . Faithing daily is how "we" die to self.