Mark 4:21, "And he said unto them, Is a candle brought to be put under a bushel, or under a bed? and not to be set on a candlestick?"
Just as a candle or lamp is not to be hid, but rather displayed so that everyone can benefit from its light, so a Christian must let his light so shine before men that they might see his good works and glorify his Father which is in heaven. God has ordained us to go and bring forth fruit (Jn. 15:16). The great commission of the Church is to reach the world.
The early Christians experienced the love of Christ in an intimate and life-transforming way. This motivated them to reach their known world with the Gospel of Christ more than any other generation of Christians has since. They didn't have the benefits of our modern technology, but they did have the benefit of being full of the love of Christ. Experiencing the love of Christ causes us to be filled with the fullness of God (Eph. 3:19) and makes us a witness that the world cannot resist (Jn. 13:35).
Today, much of the emphasis of the Church is placed on techniques of evangelism or spiritual warfare. We motivate people to witness through feelings of guilt or punishment if they don't. Much of our evangelism has become as dead and non-productive as the efforts of the cults whose people knock on doors and argue others into their way of thinking. The Church today needs a revival of our personal relationship with the Lord. When we can truly say with Paul that the love of Christ constrains us, then we will impact our world for the Lord, too. We can't give away what we don't possess. We need to personally know the love of Christ in an experiential way before we try to share it with others. Let Him love you, and let His love flow through you to others. The world is hungry for love, real love.