"You are the light of the world. A city built on a hill cannot be hid. No one after lighting a lamp puts it under a bushel basket, but on the lampstand, and it gives light to all in the house. In the same way, let your light shine before others, so that they may see your good works and give glory to your Father in heaven." - Matthew 5:14-16
It is the very property of light to SHINE. We are not given a light to shine; we ARE the light that shines. Whether we like it or not. We always shine. We shine even during the times we think we are hidden. We are still seen. It is impossible to hide ourselves. We live in a house of glass walls, essentially. How do we live? We must realize that no matter how we live each day, we still shine as a Christian. The real question is, "What am I shining out for others to see?"
You cannot cover the light, but the light can be extinguished by its own choice and desire. But when that light is actually put out....when we choose to extinguish ourselves, we are no longer followers of Christ.
The simple fact is I am a Christian, and I will shine because of it, but what do I shine forth in the name of Christianity? Since we are the actual light, we can no longer remain hidden, even if we want to.