When we live a life using Jesus as our example, we become part of his light. That's what he was trying to tell us in this verse. For those we come into contact with, and aren't familiar with Jesus or the story of the Holy Bible, we are the only example they have of what a Christian is, and what a Christian is about. It may well be our example that leads a lost soul to salvation."You are the light of the world. A town built on a hill cannot be hidden. Neither do people light a lamp and put it under a bowl. Instead they put it on its stand and it gives light to everyone in the house."~Matthew 5:14-15
Many people who didn't grow up in religious families find God and find the church through a friend. Someone they've come to know and respect--somebody they've come to trust because of the example they set. Sometimes we forget that. Sometimes we're so intent on fitting in with a group of people, whether at work or socially, that we tend to emulate the world and the culture rather than our true beliefs.
Christians have always marched to the beat of a different drummer--we were never meant to live like non-believers. We have a very different mission. The world has more than enough non-believers--what it needs is more believers! It's all of our job, not just that of our pastors, to shine that light and spread the good news.
I'm sure a lot of Christians who found the church through a friend or a co-worker or a casual acquaintance will tell you sometimes it's enough just to be a good Christian, and a good example to others. Or ask me. That's exactly how I found God in the beginning.
Take that light out from under the bowl, and put it on its stand and let the light shine to everyone around you.