Indwelling Sin in the Believer

Repent and keep repenting. As a new Christian I quickly realized that the road ahead was going to be a little harder, rather, a lot harder, than what people made it out to be. In a legalistic setting our sins carry a statute of limitations. But I have found that in actuality I am still struggling with sins that just don't want to go away.
Those sins are gone forever and we are new creation in a sense. In the sense that we are justified in Christ. Also in the since of true mortification of sins. It is true we do have a new nature and God has removed our culpability from sin.
How then do we account for sins (even familiar sin) in our Christian lives? We are not schizophrenic are we? The old nature is gone and we are created new. However, there still remains the flesh that awaits redemption. We still do things we know to be wrong ,and here in we see the unvarnished vileness of sin. There is indeed a Christian in Romans 7.
We may never be able to over come that besetting sin(s) in this life. We will never stop sinning in the here and now.
That is the goal, nevertheless i.e. mortification of sin/sanctification. Sanctification begins at conversion and continues through out our Christian life. Some times we make visible advancements in holiness while sometimes we make visible our backslidings. Let us not forget though that we are perfect already in Christ and one day our flesh will be glorified as well. "It is true this is that which is aimed at ; but this is not in this life to be accomplished" (John Owen).