I cannot be the perfect witness to my family or friends. It's not about what I do. Our salvation comes from the grace of God. In the same way, the salvation of my family and friends can only come from the grace of God. It would be an even greater example of the power of God, as well as a humbling experience for myself, when I mess up and somehow people around me are still able to know Jesus.
If I judge my fellow brothers and sisters for being poor examples of Christians, I am only downplaying who God is and I'd be limiting Him to the ability of man. But God is above all men and far more powerful. My judging does not only stem from the the inability to see the plank in my own eye, but also from my misunderstanding, of God.
"But if our unrighteousness serves to show the righteousness of God, what shall we say? That God is unrighteous to inflict wrath on us? (I speak in a human way.) By no means! For then how could God judge the world? But if through my lie God’s truth abounds to his glory, why am I still being condemned as a sinner? And why not do evil that good may come?—as some people slanderously charge us with saying. Their condemnation is just." - Romans 3:5-8