THIS is really good by Piper. I encourage you to read the summary as you watch the entire video.
Battling and killing sin is of paramount importance in the life of the believer. However, if you discipline yourself in protection apart from gospel understanding, your growth in sanctification and affection toward Christ, will be stunted. Meaning, if you do not kill sin from a grace-enabled / already-been-accepted perspective, you will inevitably try to live a moral life to hang on to God’s approval, instead of living for delight in God.
His approval is full and final in Christ. We are now free to not only battle sin, but kill it, day after day, until we escape this corrupt world for good. I meet so many people who are trying hard to live more moral than before, but they do not put the same effort into pursuing joy in Christ as they do trying to cease sinning in a particular way. Kill sin…pursue joy and your sanctification will line up more with the gospel that has set you free bonds of sin and empty pursuits.