I'm not suggesting for a moment that lust and gossip are not sinful and abhorrent to God. They are. Neither am I suggesting that we should not be seeking to put to death the sins of lust and gossip. We should. Rather, what I want to show is that we can avoid sin and still be sinning. We are not necessarily being godly when we are avoiding sin.
Let me explain. If we avoid looking lustfully at a woman or guard or tongue from gossiping because we are concerned about our reputation before others, because we want to be known in the eyes of others as godly, then we are simply replacing one sin with another. We are simply replacing the sin of lust or gossip by the sin of people pleasing and pride. We are battling sin with sin. We are letting the love of one particular idol keep us from sacrificing at the altar of another idol. In this case, our love for our reputation before others keeps us from lustful glances or gossip.
If we battle sin in this way, we may convince others and even ourselves that we are being godly. However, the truth is that we are decieving others and we are decieving ourselves. We our letting our love for one particular idol blind us to the reality of our sin. We may think that we're being godly and putting sin to death, when we are in fact letting sin flourish, we are letting a particular idol (e.g. the idol of reputation) shape our actions.
This means that as we seek to battle sin and put it to death in our lives, we need to carfully examine our motives for doing so. If we want to be godly in killing sin then we need to get our motivations right, otherwise we will only end up decieving ourselves that we are honouring God when we are not. If we are not killing sin out of a love for God which shows itself in a love for others (Matthew 22:37-40) then we are simply replacing one sin with another. A love for God which drives out a love for the world (1 John 2:15), must be the engine which drives our battle against sin. If this is not the case, then we decieve ourselves that we are being godly in our battle against sin. If we are not doing it out of a love for God, a zeal for His glory, then we will be doing it out of a love for something which is not God. This is idolatory.
The way that we cultivate a sin-killing love for God is through the gospel, as revealed in the Bible. It is by the gospel that God transforms our hearts to love Him more and more. It is as we see the glory of God in the face of Christ as revealed in the gospel (2 Corinthians 4:4, 6), that we are changed to reflect that glory more and more, because the more we see Christ, the more we will be transformed to be like Him (1 John 3:2), the only One who has perfectly loved God. As the gospel changes our hearts to love God more and more, it will simultaneously change us to hate sin more and more. This means that we will be genuinely putting sin to death and not merely replacing sin with sin.
