You may sometimes see people who pray holding hands before a meal. Everybody may recognize them as Christians. But then if they complain about the dishes, people are likely to think, 'How can Christians act like that?' It implies that people see Jesus Christ through Christians. Thus, believers in God should be aware that they are delegates of Christ and become light and salt in the world.
"For we are a fragrance of Christ to God among those who are being saved and among those who are perishing" (2 Corinthians 2:15).