When people know that we are professing Christians they'll be looking at our lives. Jesus himself established humility and gentleness as virtues. He treated people with gentleness while he healed them with God's power. His humility attracted people. While we are eager to impress people, he was eager to bless them.
Pride splits churches.
People get their toes stepped on, are rubbed the wrong way, don't feel appreciated, and then begin to gossip and complain. To achieve unity we must continually seek humility and gentleness. The desire for power is closely related to pride, and it too infects unwary believers. At the Last Supper the disciples were arguing about which of them would be considered greatest. But you are not to be like that.