Is this the way to think of sin in believers?
The Presence of Sin: Completely Present
The Penalty of Sin: Completely Gone
The Power of Sin: Progressively Weakened
A Christian, then, is someone who has had the condemnation of sin removed, while experiencing increasing freedom from sin's hold, while not knowing total freedom until the next life. That is, the penalty of sin has been killed in the past, the power of sin is being killed in the present, and the presence of sin will be killed in the future.
Another important variable, when we enfold unbelievers into the discussion, is the image of God, which is manifestly present in all, believer and unbeliever. This helps us avoid extremes. Remembering the presence of sin in believers keeps us from over-optimism regarding the Christian life, while remembering the imago dei in unbelievers keeps us from over-pessimism regarding the non-Christian life. Unbelievers are not as bad as they might be; believers are not as good as they will be.