Body of believers

Am I not called to encourage my brothers and sisters in Christ to live Godly lives? Am I not told to address areas of sin or causing of sin in lives of fellow believers? Am I not expected to help a part of the body to live for Christ?

What if the part doesn't listen? What if the part doesn't see the need to change? What if the part doesn't see the potential for glorifying God even more?

How much should I challenge the part? How much should I let God mold the part? What am I supposed to do?