We have an enemy that speaks lies to us, we have the world with it's way of living, and we have the flesh which has the power if sin in it. The flesh is a left over of the old man's ( which has been crucified with Christ and now e have a new man ) way of thinking, habits, ways of acting, our un-renewed beliefs in our brain.
The flesh and the power of sin in it ..are in cahoots together to derail your thinking ( to keep your thoughts from believing your true identity in Christ )
The power of sin in you knows what works on you. Whatever areas of your life that you have struggled with is what "sin" brings to you.
The power of sin then condemns you..saying you are unworthy, guilty, etc. The Holy Spirit is in us to tell us that we have in fact a new identity in Christ. He will tell you that you are the righteousness of God in Christ...the Holy Spirit will tell you who you really are because of Christ's perfect sacrifice for you!