No more quickly can a person rob you of your joy and peace than when that individual succeeds at making you feel like you're less than worthy of God as compared to his/her own self. The old adage "You're on your way to hell, and I'm on my way to heaven" spoken or implied to another, is the most predominantly effective way to make someone feel better about himself; and he doesn't even have to prove he's better in this life on earth because now he can just say "Wait 'til I'm looking down at you while you're in hell!" But don't be robbed of your joy and peace, individuals or groups of people like that don't know where God is; He is a whisper-distance away from you, is all.