Be killing sin!

"...the choicest believers, who are assuredly freed from the condemning power of sin, ought yet to make it their business all their days to mortify the indwelling power of sin...Do you mortify; do you make it your daily work; be always at it whilst you live; cease not a day from this work; be killing sin or it will be killing you. Your being dead with Christ virtually, your being quickened with him, will not excuse you from this work."

From Mortification of Sin, by John Owen.