That's true, but what I said was for those who think they can only just live a good life and expect people to be falling on their knees in repentance around them due to their perfect lives and little halo on their head. It doesn't happen like that at all.
There are moral atheists and godly muslims around who live great moral lives and are held in high regard by men. Some even more righteous than the average Christian (self-righteousness, of course). So the Christian is competing with these and thats why living a good life will not save many.
Even if our life doesn't match our words, and truly, I don't know many christians who are that perfect, we can still declare the Gospel as God's mouthpiece.
In the biblical concept of witnessing, witnessing does not mean testifying of what God has done in your life. It means witnessing the cross of Christ. And the early witnesses, the disciples, were real witnesses of Christ crucified, as they saw it with their own eyes.
When we say to someone "look what Christ has done in my life", they may reply, "yes, so and so Muslim has had the same or similar effect, or so and so Hare Krishna has found peace and joy in their life too".