I once heard (and I've often repeated it) that if repentance and faith are step one in our Christian walk then step two is repeat step one. Not a day goes by that we do not have to fight sin. There is a choice to make- pursue it or kill it. Every day we must- by the power of the indwelling Holy Spirit- turn from self and trust Christ our Lord. These sermons by John Piper will challenge and convict you to make war against sin.
How to Kill Sin (part one)
How to Kill Sin (part two)