I wouldn't put so much focus on sin, as I would on Christ. The blood of Jesus has granted you the remission of your sins. In Christ, you are forgiven and there is no condemnation. This is you being justified before God. A righteous standing. As for your sin, and how to practically overcome sin, this is God's doing. Yes, and your surrender, your willingness to change and, again, approach the throne of grace.
Your sin as ugly as it is, God wants better for you. He doesn't hold the sin against you, but rather would encourage you to walk in the light. You don't have to entertain that particular sin. You don't. That you think you do is where you're deceived, and for that reason of deception do you continue to fall.
You may feel weak, but this is why you approach the throne of grace, to obtain mercy and find grace in time of need.